Insulation monitoring system and control method thereof

Abstract

An insulation monitoring system according to an embodiment of the present invention comprises: an arc monitoring unit which detects a high-frequency current signal from a power line connecting a power source and a load, and monitors generation of an arc due to insulation damage of the power line on the basis of the detected high-frequency current signal; an insulation monitoring unit which calculates an insulation resistance between the power line and a ground, and monitors an insulation state of the power line on the basis of the calculated insulation resistance; a circuit breaker which breaks an electrical connection between the power line and the load according to whether a blocking signal is received; and a control unit which is connected to the arc monitoring unit and the insulation monitoring unit, receives at least one of an insulation monitoring result related to generation of the arc from the arc monitoring unit and an insulation monitoring result related to the insulation resistance from the insulation monitoring unit, and outputs the blocking signal to the circuit breaker on the basis of the received insulation monitoring result.

Description

Insulation monitoring system and control method thereof

[0001] The present invention relates to a system for monitoring the insulation status of a power line.

[0002] Typically, an insulation monitoring device (IMD) is placed between a ground and an ungrounded power line that is supplied with power, and a pulse signal generating unit applies a square wave pulse signal (voltage: Vp) to a circuit formed between the power line and the ground, calculates the insulation resistance (Re) based on a signal (voltage: Vm) in which voltage is distributed by a virtual resistance (insulation resistance (Re)) between the power line and the ground and the internal resistance (Ri) of the insulation monitoring device from the applied pulse signal (Vp), and compares the size of the calculated insulation resistance with a reference value, thereby enabling the insulation status of the power line to be monitored.

[0003] In order to calculate the above insulation resistance, the pulse signal generation unit must inject a pulse signal whose polarity is reversed into the circuit at regular intervals. However, since a virtual capacitance, i.e., an insulating capacitor, exists between the power line and the ground, when the polarity of the pulse signal is reversed, the voltage difference of the reversed pulse signal causes charging and discharging of the insulating capacitor, which causes a transient phenomenon in which the voltage increases and becomes unstable. This transient phenomenon is temporary, and the voltage becomes stable again after a certain period of time has passed until the charging and discharging of the insulating capacitor is completed.

[0004] However, in the above transient state, the insulation resistance of the power line to be measured and the insulation capacitance components are mixed, resulting in a large error. Therefore, it is difficult to accurately calculate the insulation resistance, and thus, conventional insulation monitoring devices calculate the insulation resistance after the transient phenomenon has ended, that is, after the transient period has elapsed and the voltage has stabilized.

[0005] Accordingly, in the case of conventional insulation monitoring devices, there is a problem that a relatively long time is required until the insulation resistance is calculated after the voltage polarity of the pulse signal is reversed. Since it takes a long time to calculate the insulation resistance, the insulation status of the power line according to the insulation resistance cannot be detected during the time until the insulation resistance is calculated, i.e., during the voltage stabilization period, and thus, there is a problem that the power equipment is vulnerable to damage or safety accidents due to ground fault current caused by insulation breakdown or insulation damage (hereinafter collectively referred to as insulation breakdown).

[0006] Meanwhile, for the above voltage stabilization, a conventional insulation monitoring device waits until an initial waiting time has elapsed after the polarity of the pulse signal has been reversed, and then performs sampling after the initial waiting time has elapsed to determine whether the voltage has stabilized. Therefore, there is a problem in that it is difficult to monitor the insulation of a power line during the time between the polarity of the pulse signal being reversed and the voltage being stabilized.

[0007] Meanwhile, if insulation breakdown occurs in a power line, or if a connection defect or aging occurs, an arc may occur in the power line. The arc refers to an electric spark or spark, and refers to a discharge phenomenon that occurs when a high voltage difference occurs between the positive and negative terminals, and is characterized by a high current density.

[0008] These arcs are known to be a major cause of electrical fires, as they can cause fires if there is ignitable material nearby. These arcs are currently detected by leakage current circuit breakers or overcurrent circuit breakers when a certain amount of current is detected, thereby determining it as a leakage current or overcurrent.

[0009] However, arcs can occur even at low currents of 3 to 5 A, making them difficult to detect with leakage circuit breakers or overcurrent circuit breakers. Therefore, many countries are mandating the installation of arc circuit breakers capable of interrupting such arcs, and active research is underway to detect and block arcs.

[0010] The present invention is intended to solve the above-mentioned problem, and provides an insulation monitoring system capable of monitoring the insulation status of a power line even during the voltage stabilization period, and a control method of the system.

[0011] In addition, another object of the present invention is to provide an insulation monitoring system capable of monitoring not only the insulation status of a power line but also an arc occurring due to insulation breakdown of the power line, and a control method of the system.

[0012] In addition, another object of the present invention is to provide an insulation monitoring system and a control method thereof capable of monitoring the insulation status of the power line through an insulation monitoring function that combines the insulation monitoring function and the arc monitoring function, and more quickly cutting off the electrical connection with the power line when an insulation breakdown is detected.

[0013] In addition, another object of the present invention is to provide an insulation monitoring device that not only calculates the insulation resistance of a power line to monitor the insulation status of the power line, but also monitors whether an arc occurs in the power line, and a control method of the device.

[0014] In addition, another object of the present invention is to provide an insulation monitoring device and a control method thereof that can minimize the time during which insulation monitoring is not performed by the insulation monitoring device by monitoring the insulation status of the power line through the arc monitoring during a period during which the insulation monitoring device is unable to monitor the insulation status of the power line.

[0015] In order to achieve the above-described object, an insulation monitoring system according to an embodiment of the present invention includes an arc monitoring unit that detects a high-frequency current signal from a power line connecting a power source and a load and monitors the occurrence of an arc due to insulation damage of the power line based on the detected high-frequency current signal; an insulation monitoring unit that calculates insulation resistance between the power line and ground and monitors the insulation status of the power line based on the calculated insulation resistance; a circuit breaker that cuts off the electrical connection between the power line and the load depending on whether a cut-off signal is received; and a control unit that is connected to the arc monitoring unit and the insulation monitoring unit and receives at least one of an insulation monitoring result related to the occurrence of the arc from the arc monitoring unit and an insulation monitoring result related to the insulation resistance from the insulation monitoring unit, and outputs the cut-off signal to the circuit breaker based on the received insulation monitoring result.

[0016] In one embodiment, the insulation monitoring result received from the arc monitoring unit includes a signal intensity change pattern of a high-frequency current signal detected from the power line, and the control unit is characterized in that it determines the insulation state of the power line based on whether the signal intensity change pattern matches a previously stored arc pattern.

[0017] In one embodiment, the signal intensity change pattern is a pattern according to an intensity change of a high-frequency current signal detected at each of a first point in time when the AC current flowing in the power line reaches a ZCP (Zero Crossing Point), a second point in time between a third point in time corresponding to 1 / 4 cycle of the AC current, and a fourth point in time between the third point in time and the point in time when the ZCP is reached again, and the arc pattern is characterized in that it is a pattern corresponding to a step-by-step signal intensity change of a high-frequency current signal that occurs when an arc occurs in the power line.

[0018] In one embodiment, the arc monitoring unit is characterized in that it obtains a preset number of intensity samples of the high-frequency current signal based on each of the first to fourth time points, averages the obtained samples for each time point to calculate a signal intensity average for each time point, and detects a pattern in which the calculated signal intensity average for each time point changes as the signal intensity change pattern.

[0019] In one embodiment, the control unit is characterized in that, when the signal intensity change pattern matches the pre-stored arc pattern, it determines whether the signal intensity change pattern detected from the high-frequency current signal for a certain period of time matches the pre-stored arc pattern a preset number of times, and determines the insulation state of the power line based on the determination result.

[0020] In one embodiment, the insulation monitoring result received from the arc monitoring unit includes the magnitude of frequency components included in at least one preset frequency band among the frequency components of a high-frequency current signal detected from the power line, and the control unit is characterized in that it monitors the insulation status of the power line based on the magnitude of the frequency components included in the insulation monitoring result.

[0021] In one embodiment, the arc monitoring unit is characterized by comprising: a High Frequency Current Transformer (HFCT) for detecting the high frequency current signal from the power line; a Fast Fourier Transformer (FFT) for decomposing the high frequency current signal into a magnitude for each frequency component; a memory including information on at least one frequency band related to a high frequency current signal generated when an arc occurs; and an arc monitoring control unit for detecting, among each frequency component of the decomposed high frequency current signal, at least one frequency component included in at least one frequency band stored in the memory and transmitting the insulation monitoring result including the magnitude of the detected frequency components to the control unit.

[0022] In one embodiment, the insulation monitoring unit is characterized in that, when the polarity of a pulse signal applied to the power line is reversed, it transmits a notification signal notifying the polarity reversal to the control unit, and when the insulation resistance corresponding to the pulse signal whose polarity is reversed is calculated, it transmits the calculated insulation resistance to the control unit.

[0023] In one embodiment, the control unit is characterized in that, when the notification signal is received from the insulation monitoring unit, the control unit monitors the insulation status of the power line based on the insulation monitoring result received from the arc monitoring unit until the insulation resistance calculated by the insulation monitoring unit is received, and when the insulation resistance is received, the control unit monitors the insulation status of the power line based on the insulation monitoring result received from the insulation monitoring unit.

[0024] In one embodiment, the circuit breaker includes at least one semiconductor switch including a source terminal connected to a power side of the power line, a drain terminal connected to a load side of the power line, and a gate terminal electrically connecting the source terminal and the drain terminal based on an applied gate voltage, and a gate driver applying the gate voltage to the gate terminal, wherein the control unit is characterized in that it controls the gate driver to apply a gate voltage less than a preset threshold voltage based on an insulation monitoring result received from at least one of the arc monitoring unit and the insulation monitoring unit.

[0025] In order to achieve the above-described object, a control method of an insulation monitoring system according to an embodiment of the present invention comprises the steps of: when the insulation monitoring unit reverses the polarity of a pulse signal applied to the power line for calculating insulation resistance, transmitting a notification signal to the blocking unit for notifying the polarity reversal of the pulse signal; when the blocking unit receives the notification signal, receiving a first insulation monitoring result related to the occurrence of the arc from the arc monitoring unit; a step for the blocking unit to determine the insulation state of the power line based on the first insulation monitoring result; a step for the blocking unit to disconnect a load from the power line if insulation damage is detected as a result of the insulation state determination according to the first insulation monitoring result; a step for the insulation monitoring unit to calculate insulation resistance and transmit the calculated insulation resistance to the blocking unit while the blocking unit determines the insulation state of the power line based on the first insulation monitoring result; and a step for the blocking unit to receive insulation resistance and re-determine the insulation state of the power line based on the received insulation resistance if insulation damage is not detected as a result of the insulation state determination according to the first insulation monitoring result. And, the blocking unit is characterized by including a step of blocking the load from the power line according to the result of the trial.

[0026] In one embodiment, the step of the blocking unit determining the insulation state of the power line based on the first insulation monitoring result includes the step of the blocking unit receiving, from the arc monitoring unit, a signal intensity change pattern of a high-frequency current signal detected in the power line, and the step of the blocking unit determining whether the received signal intensity change pattern matches a pre-stored arc pattern, wherein the signal intensity change pattern is a pattern according to an intensity change of a high-frequency current signal detected at each of a first point in time when an AC current flowing in the power line reaches a ZCP (Zero Crossing Point), a second point in time between a third point in time corresponding to 1 / 4 cycle of the AC current, and a fourth point in time between the third point in time and the point in time when the ZCP is reached again, and the arc pattern is characterized in that it is a pattern corresponding to a stepwise signal intensity change of a high-frequency current signal that occurs when an arc occurs in the power line.

[0027] In one embodiment, the step of the blocking unit determining the insulation state of the power line based on the first insulation monitoring result is characterized in that the step includes the steps of: the blocking unit further detecting signal intensity change patterns of the high-frequency current signal for a predetermined period of time when the signal intensity change pattern matches the pre-stored arc pattern; the step of the blocking unit detecting the number of times the signal intensity change patterns detected for the predetermined period of time match the arc pattern; and the step of the blocking unit determining the insulation state of the power line based on whether the number of times the detection reaches a preset number.

[0028] In one embodiment, the step of determining the insulation state of the power line based on the first insulation monitoring result by the blocking unit includes the step of the blocking unit receiving the magnitude of at least one preset frequency component from the arc monitoring unit, and the step of the blocking unit determining the insulation state of the power line based on the magnitude of the received frequency components, wherein the magnitude of the frequency components received from the arc monitoring unit are frequency components extracted by the arc monitoring unit based on at least one frequency band related to arc occurrence among the frequency components of a high-frequency current signal detected from the power line.

[0029] In order to achieve the above or other purposes, according to one aspect of the present invention, an insulation monitoring device according to an embodiment of the present invention is characterized by including an arc monitoring unit that detects a high-frequency current signal from a power line connecting a power source and a load and collects an analysis result of analyzing the detected high-frequency current signal, an insulation monitoring unit that calculates insulation resistance between the power line and ground, a blocking unit that blocks the connection between the power source and the load, and a control unit that determines the insulation state of the power line using either the analysis result of the high-frequency current signal or the insulation resistance based on a polarity inversion time from when the voltage polarity of a pulse signal applied by the insulation monitoring unit to the power line is inverted to when the voltage polarity is inverted again, an initial waiting time from when the voltage polarity of the pulse signal is inverted until initial sampling is performed, and whether or not the insulation resistance is calculated, and controls the blocking unit so that the connection between the power source and the load is blocked based on the determination result.

[0030] In one embodiment, the analysis result of analyzing the high-frequency current signal includes a signal intensity change pattern of the high-frequency current signal detected from the power line, and the control unit is characterized in that it determines the insulation state of the power line based on whether the signal intensity change pattern matches a previously stored arc signal intensity change pattern.

[0031] In one embodiment, the signal intensity change pattern is a pattern according to an intensity change of a high-frequency current signal detected at each of a first point in time when the AC current flowing in the power line reaches a ZCP (Zero Crossing Point), a second point in time between a third point in time corresponding to 1 / 4 cycle of the AC current, and a fourth point in time between the third point in time and the point in time when the ZCP is reached again, and the arc signal intensity change pattern is characterized in that it is a pattern corresponding to a stepwise signal intensity change of a high-frequency current signal that occurs when an arc occurs in the power line.

[0032] In one embodiment, the arc monitoring unit is characterized in that it obtains a preset number of intensity samples of the high-frequency current signal based on each of the first to fourth time points, averages the obtained samples for each time point to calculate an average signal intensity for each time point, and detects a pattern in which the average signal intensity for each time point changes as the signal intensity change pattern.

[0033] In one embodiment, the control unit is characterized in that, when the signal intensity change pattern matches the pre-stored arc signal intensity change pattern, the control unit determines the insulation state of the power line based on a result of determining whether the signal intensity change pattern detected from the high-frequency current signal for a certain period of time matches the pre-stored arc signal intensity change pattern a preset number of times.

[0034] In one embodiment, the analysis result of analyzing the high-frequency current signal includes the magnitude of frequency components detected based on at least one preset frequency band among the frequency components of the high-frequency current signal detected from the power line, and the control unit is characterized in that it monitors the insulation state of the power line based on the magnitude of the detected frequency components.

[0035] In one embodiment, the arc monitoring unit is characterized by including a High Frequency Current Transformer (HFCT) that detects the high frequency current signal from the power line, and a Fast Fourier Transformer (FFT) that decomposes the high frequency current signal into magnitudes for each frequency component.

[0036] In one embodiment, the control unit is characterized in that, when the initial waiting time has elapsed, the control unit controls the insulation monitoring unit to calculate insulation resistance, and determines the insulation state of the power line based on the calculated insulation resistance, and when the insulation resistance has been calculated, the voltage polarity of the pulse signal is reversed again, and then, for the pulse signal whose voltage polarity has been reversed, the insulation state of the power line is determined based on an analysis result of analyzing the high-frequency current signal received from the arc monitoring unit until the initial waiting time has elapsed again.

[0037] In one embodiment, the blocking unit includes at least one semiconductor switch including a source terminal connected to the power side of the power line, a drain terminal connected to the load side of the power line, and a gate terminal electrically connecting the source terminal and the drain terminal based on an applied gate voltage, and a gate driver that applies the gate voltage to the gate terminal, and the control unit is characterized in that it controls the gate driver to apply a gate voltage less than a preset threshold voltage based on one of the analysis results of the high-frequency current signal and the insulation resistance.

[0038] In order to achieve the above or other purposes, according to one aspect of the present invention, a control method of an insulation monitoring device according to an embodiment of the present invention includes a step of checking whether a first condition, which is satisfied depending on whether a time elapsed from the time a pulse signal having a positive or negative voltage of a certain magnitude is applied to a power line has passed a preset initial waiting time, and a second condition, which is satisfied depending on whether insulation resistance has been calculated, are both satisfied; a step of determining whether an arc has occurred in the power line based on a high-frequency current signal detected from the power line until both the first and second conditions are satisfied if both the first and second conditions are not satisfied; a step of calculating insulation resistance between the power line and ground if both the first and second conditions are satisfied in a state where an arc has not occurred as a result of determining whether an arc has occurred; a step of determining an insulation state of the power line based on the magnitude of the calculated insulation resistance when the insulation resistance is calculated; and a step of checking whether both the first and second conditions have been satisfied based on the result of determining the insulation state or the step of determining the insulation state of the power line based on the magnitude of the insulation resistance are repeatedly performed. It is characterized by.

[0039] In one embodiment, the step of determining whether an arc has occurred further includes a step of cutting off the electrical connection between the power source and the load if it is determined as a result of the determination of whether an arc has occurred that an arc has occurred, and the step of determining the insulation status further includes a step of cutting off the electrical connection between the power source and the load if the insulation of the power line is damaged.

[0040] In one embodiment, the step of checking whether both the first and second conditions are satisfied further includes the step of checking whether a preset polarity inversion time of a pulse signal has elapsed, and the step of inverting the voltage polarity of the pulse signal if the polarity inversion time has elapsed, wherein the required time is initialized if the polarity inversion time has elapsed.

[0041] In one embodiment, the step of determining whether an arc has occurred in the power line includes a step of detecting a signal intensity change pattern of a high-frequency current signal detected in the power line, and a step of determining whether the arc has occurred based on whether the detected signal intensity change pattern matches a previously stored arc signal intensity change pattern, wherein the signal intensity change pattern is a pattern according to an intensity change of a high-frequency current signal detected at each of a first point in time when an AC current flowing in the power line reaches a ZCP (Zero Crossing Point), a second point in time between a third point in time corresponding to 1 / 4 cycle of the AC current, and a fourth point in time between the third point in time and the point in time when the ZCP is reached again, and the arc signal intensity change pattern is characterized in that it is a pattern corresponding to a stepwise signal intensity change of a high-frequency current signal that occurs when an arc has occurred in the power line.

[0042] In one embodiment, the step of determining whether an arc has occurred based on the detected signal intensity change pattern is characterized in that the step further includes the steps of: re-detecting signal intensity change patterns of the high-frequency current signal for a predetermined period of time when the signal intensity change pattern matches the previously stored arc signal intensity change pattern; detecting the number of times the re-detected signal intensity change patterns match the arc signal intensity change pattern; and determining whether an arc has occurred based on whether the number of times the detected number reaches a preset number.

[0043] In one embodiment, the step of determining whether an arc has occurred in the power line is characterized by including a step of performing a fast Fourier transform on the high-frequency current signal to decompose the high-frequency current signal into each frequency component, a step of detecting frequency components included in at least one previously stored frequency band among the decomposed frequency components, and a step of determining whether the arc has occurred based on the magnitude of the detected frequency components.

[0044] The insulation monitoring system according to the present invention and the effects of the insulation monitoring system are described as follows.

[0045] According to at least one of the embodiments of the present invention, the present invention includes an insulation monitoring unit that calculates the insulation resistance of a power line and an arc monitoring unit that can detect an arc that occurs when the insulation of the power line is broken, thereby detecting the insulation status of the power line through the insulation resistance of the power line and simultaneously detecting whether an arc occurs in the power line.

[0046] In addition, according to at least one of the embodiments of the present invention, the present invention monitors whether an arc occurs in a power line through the arc monitoring unit during the voltage stabilization period required until the insulation resistance is calculated by the insulation monitoring unit, thereby monitoring the insulation state of the power line, and when the voltage stabilization period is completed and the insulation resistance is calculated by the insulation monitoring unit, the insulation state of the power line is monitored based on the calculated insulation resistance, thereby enabling the insulation state of the power line to be continuously monitored without a gap.

[0047] In addition, according to at least one of the embodiments of the present invention, the present invention includes a semiconductor circuit breaker including a power semiconductor, and a control unit of the semiconductor circuit breaker controls the semiconductor circuit breaker according to insulation status information received from the arc monitoring unit and the insulation monitoring unit, thereby enabling faster control of electrical connection with the power line. Accordingly, there is an effect of more effectively preventing damage to power equipment or safety accidents due to insulation breakdown.

[0048] According to at least one of the embodiments of the present invention, the present invention has the effect of being able to monitor both the insulation status of a power line and whether an arc occurs using a single device, without installing an arc monitoring device separately from an insulation monitoring device.

[0049] In addition, according to at least one of the embodiments of the present invention, the present invention has the effect of minimizing the time during which insulation monitoring is not performed by the insulation monitoring device by enabling the insulation status of the power line to be monitored through the arc monitoring during a period during which the insulation monitoring device is unable to monitor the insulation status of the power line.

[0050] FIG. 1 is a block diagram illustrating the configuration of an insulation monitoring system according to an embodiment of the present invention.

[0051] FIG. 2a is a block diagram illustrating the configuration of an arc monitoring unit that monitors an arc of an alternating current in an insulation monitoring system according to an embodiment of the present invention.

[0052] FIG. 2b is an exemplary diagram showing an example of a high-frequency current signal detected by an arc monitoring unit according to an embodiment of the present invention in a state where an arc has occurred.

[0053] FIG. 3 is a block diagram illustrating the configuration of an arc monitoring unit that monitors a DC current arc in an insulation monitoring system according to an embodiment of the present invention.

[0054] FIG. 4 is a block diagram illustrating the configuration of an insulation monitoring unit of an insulation monitoring system according to an embodiment of the present invention.

[0055] FIG. 5 is a block diagram illustrating the configuration of a blocking unit of an insulation monitoring system according to an embodiment of the present invention.

[0056] FIG. 6 is a flowchart illustrating an operation process in which an arc monitoring unit, an insulation monitoring unit, and a cutoff unit are linked in an insulation monitoring system according to an embodiment of the present invention.

[0057] FIG. 7 is a flowchart illustrating the operation process of a circuit breaker that performs insulation monitoring using an arc monitoring unit and an insulation monitoring unit according to a voltage stabilization period in an insulation monitoring system according to an embodiment of the present invention.

[0058] Fig. 8 is an exemplary diagram showing an example in which insulation monitoring is performed according to whether an arc occurs and insulation resistance according to the voltage stabilization period according to the operation process of Fig. 7.

[0059] FIG. 9 is a flowchart illustrating another operation process in which an arc monitoring unit, an insulation monitoring unit, and a circuit breaker unit are linked in an insulation monitoring system according to an embodiment of the present invention.

[0060] FIG. 10 is a flowchart illustrating another operation process of a circuit breaker that performs insulation monitoring using an arc monitoring unit and an insulation monitoring unit according to a voltage stabilization period in an insulation monitoring system according to an embodiment of the present invention.

[0061] FIG. 11a is a block diagram illustrating the configuration of an insulation monitoring device according to an embodiment of the present invention.

[0062] FIG. 11b is a conceptual diagram illustrating an example in which an arc monitoring unit and an insulation monitoring unit of an insulation monitoring device according to an embodiment of the present invention are connected to a power line.

[0063] FIG. 12a is a block diagram illustrating components of an arc monitoring unit according to an embodiment of the present invention.

[0064] FIG. 12b is a block diagram illustrating components of an insulation monitoring unit according to an embodiment of the present invention.

[0065] Fig. 13 is a block diagram showing a detailed configuration of a blocking unit of an insulation monitoring device according to an embodiment of the present invention.

[0066] Figure 14 is a flowchart illustrating the operation process of an insulation monitoring device according to an embodiment of the present invention.

[0067] FIG. 15a is a flowchart illustrating the operation process of an arc monitoring unit that monitors an arc of an alternating current during the operation process of an insulation monitoring device according to an embodiment of the present invention.

[0068] FIG. 15b is an exemplary diagram showing an example of a high-frequency current signal detected by an arc monitoring unit according to an embodiment of the present invention in a state where an arc has occurred.

[0069] FIG. 16 is a flowchart illustrating the operation process of an arc monitoring unit that monitors a DC arc during the operation process of an insulation monitoring device according to an embodiment of the present invention.

[0070] Figure 17 is a conceptual diagram for explaining that arc monitoring and insulation monitoring are performed by an insulation monitoring device according to an embodiment of the present invention.

[0071] It should be noted that the technical terms used herein are used merely to describe specific embodiments and are not intended to limit the present invention. Furthermore, singular expressions used herein include plural expressions unless the context clearly dictates otherwise. The suffixes "module" and "part" used in the following description for components are assigned or used interchangeably solely for the convenience of writing the specification, and do not in themselves have distinct meanings or roles.

[0072] In this specification, the terms “comprises” or “includes” should not be construed to necessarily include all of the components or steps described in the specification, and some of the components or steps may not be included, or additional components or steps may be included.

[0073] In addition, when describing the technology disclosed in this specification, if it is determined that a detailed description of a related known technology may obscure the gist of the technology disclosed in this specification, the detailed description is omitted.

[0074] In addition, the attached drawings are only intended to facilitate easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings, and should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention. In addition, not only each embodiment described below, but also a combination of embodiments may correspond to the spirit and technical scope of the present invention as modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

[0075] First, FIG. 1 is a block diagram illustrating the configuration of an insulation monitoring system according to an embodiment of the present invention.

[0076] Referring to FIG. 1, an insulation monitoring system (1) according to an embodiment of the present invention may be configured to include an insulation monitoring unit (30) that monitors the insulation status of a power line (50), an arc monitoring unit (20) that monitors whether an arc occurs in the power line (50) based on a high-frequency current signal, and a blocking unit (10) that blocks the connection between the power line (50) and a load based on a blocking signal received from the insulation monitoring unit (30) and the arc monitoring unit (20). Here, the power line (50) may be a power line through which power is supplied from an ungrounded (IT: Insulation Terra) power system.

[0077] The above-described blocking unit (10) may be provided on a power line connecting a power source and a load or a power line connecting a system to a system. That is, when the left side of the blocking unit (10) in FIG. 1, i.e., A, is connected to a power source, the right side of the blocking unit (10), i.e., B, may be connected to a load. Conversely, when the right side (B) of the blocking unit (10) in FIG. 1 is connected to a power source, the left side (A) of the blocking unit (10) may be connected to a load. In this way, when one side is a power source and the other side is a load, a one-way current flow may be formed. In addition, the A and B may be different power systems, such as different microgrids, in which case a two-way current flow may be formed not only from system A to system B, but also from system B to system A.

[0078] To connect or block such one-way or two-way current flow, the blocking unit (10) may include a semiconductor circuit breaker (110) including at least one semiconductor switch. In addition, the blocking unit (10) may include a control unit (100) for controlling the semiconductor circuit breaker (110).

[0079] The control unit (100) may be connected to the insulation monitoring unit (30) and the arc monitoring unit (20) by wire or wireless communication, and may receive a monitoring result from at least one of the insulation monitoring unit (30) and the arc monitoring unit (20) through the communication connection. Then, the semiconductor circuit breaker (110) may be controlled to perform a blocking operation based on the received monitoring result. Accordingly, a load may be blocked from the power line (50) or another system (e.g., system B) may be blocked from a system in which insulation has been broken (e.g., system A) depending on the monitoring result of either the arc monitoring unit (20) or the insulation monitoring unit (30). The operation process of the blocking unit (10) according to the embodiment of the present invention will be described in more detail with reference to FIG. 5 below.

[0080] Alternatively, the control unit (100) may control the connected arc monitoring unit (20) and insulation monitoring unit (30). For example, the control unit (100) may determine whether the insulation monitoring unit (30) is in a state where it can calculate insulation resistance based on the state of the insulation monitoring unit (30). In addition, if the insulation monitoring unit (30) is in a state where it cannot monitor the insulation state of the power line (50), the control unit (100) may control the arc monitoring unit (20) to monitor whether the insulation of the power line (50) is broken by determining whether an arc occurs.

[0081] Meanwhile, if the insulation monitoring unit (30) is capable of calculating the insulation resistance as a result of the status determination of the insulation monitoring unit (30), the control unit (100) can also monitor the insulation status of the power line (50) based on the insulation resistance calculated by the insulation monitoring unit (30). In this case, during a time when the insulation monitoring unit (30) cannot monitor the insulation status of the power line (50), such as a voltage stabilization time, whether or not the insulation of the power line (50) is broken is monitored based on the monitoring result of the arc monitoring unit (20), and if the insulation monitoring unit (30) can monitor the insulation status of the power line (50) through the calculated insulation resistance, the insulation status of the power line (50) can be monitored based on the monitoring result of the insulation monitoring unit (30), i.e., the insulation resistance. That is, the insulation status of the power line (50) can be monitored without a blank period in which the insulation status is not detected. The operation process of the blocking unit (10) according to this embodiment of the present invention will be examined in more detail with reference to FIG. 7 below.

[0082] Hereinafter, with reference to FIGS. 2a to 4, a more detailed configuration of the arc monitoring unit (20), insulation monitoring unit (30), and blocking unit (10) will be examined.

[0083] First, Fig. 2a is a block diagram illustrating the configuration of an arc monitoring unit (20) of an insulation monitoring system (1) according to an embodiment of the present invention. Fig. 2a illustrates an example of an arc monitoring unit (20) that detects an arc based on a partial discharge that occurs when insulation is broken when the power line (50) is a circuit through which an alternating current flows. In addition, Fig. 2b is an exemplary diagram illustrating an example of a high-frequency current signal detected by the arc monitoring unit according to an embodiment of the present invention when an arc has occurred.

[0084] First, referring to FIG. 2a, the arc monitoring unit (20) may be formed by including a high frequency current transformer (HFCT) (210) for detecting a high frequency current signal, a filter unit (220) for frequency filtering, a signal intensity detection unit (power detector) (230) for detecting the signal intensity of the high frequency current signal, and an amplifier unit (240) for amplifying the signal level of the high frequency current signal detected by the signal intensity detection unit (230) into a signal of a size that can be identified by the arc monitoring control unit (200-1), and the arc monitoring control unit (200-1). In addition, the arc monitoring control unit (200-1) may include a voltage detection unit (250) for detecting a voltage change of the power line (50).

[0085] More specifically, the HFCT (210) can detect a high-frequency current signal from a power line (50). The high-frequency current signal is a signal in a high-frequency band generated by partial discharge caused by an arc, and may also be referred to as a high-frequency noise signal.

[0086] And the filter unit (220) may be a filter that filters a specific frequency in a frequency mask manner. Here, the specific frequency may be a frequency corresponding to living noise, noise generated when driving a load, or electromagnetic noise (EMC (ElectroMagnetic Compatibility) Noise). The filter unit (220) is a filter that filters signals of at least one different frequency band that is designated in advance, and can remove noise whose frequency band is known in advance, such as living noise, driving noise of a load, or electromagnetic noise.

[0087] The signal intensity detection unit (230) can detect the intensity of the high-frequency current signal detected through the HFCT (210). For example, the signal intensity detection unit (230) can convert the high-frequency current signal detected by the HFCT (210) into a voltage signal corresponding to its intensity. Here, since the high-frequency current signal converted into the voltage signal may be an analog signal, the signal intensity detection unit (230) may further include an analog-to-digital converter (ADC) for converting the high-frequency current signal in the analog form into a digital signal. Accordingly, the high-frequency current signal converted into the voltage signal can be converted into a digital signal having different values ​​depending on the signal intensity through the signal intensity detection unit (230).

[0088] The amplifier (240) can receive a digital signal input from the signal intensity detection unit (230) and amplify the received digital signal into a signal of a level identifiable by the arc monitoring control unit (200-1). Here, the amplifier (240) can be an inverting amplifier that inverts the phase of an input signal and amplifies the inverted signal phase according to a voltage gain having a negative (-) value, or a non-inverting amplifier that maintains the phase of an input signal as it is and amplifies only the magnitude thereof according to a voltage gain having a positive (+) value.

[0089] Meanwhile, the voltage detection unit (250) can detect a voltage change of the power line (50). In this case, if the current flowing in the power line (50) is a single-phase current, the current flowing in the power line may be a current in which the positive (+) voltage and the negative (-) voltage periodically change according to the cycle of the single-phase current. Accordingly, the voltage change in which the positive (+) voltage and the negative (-) voltage periodically change can be detected through the voltage detection unit (150) and provided to the arc monitoring control unit (200-1).

[0090] Meanwhile, the arc monitoring control unit (200-1) controls each connected component and can control the overall operation of the arc monitoring unit (20). The arc monitoring control unit (200-1) can detect the point in time when the voltage changes from a positive (+) value to a negative (-) value, or from a negative value to a positive value, i.e., the zero crossing point, based on the voltage change detected through the voltage detection unit (250).

[0091] And the arc monitoring control unit (200-1) can receive the amplified high-frequency current signal through the amplifier unit (240). And it can detect the change in the intensity of the high-frequency current signal over time. In addition, the arc monitoring control unit (200-1) can detect the change in the intensity of the high-frequency current signal corresponding to the half cycle of the current flowing in the power line (50) based on the zero crossing points detected through the voltage detection unit (150). And, according to the pattern indicated by the change in the intensity of the high-frequency current signal during the detected half cycle, it can be determined whether an arc occurred in the power line (50) during the half cycle.

[0092] For example, when an arc occurs, the high-frequency current signal may have a periodic characteristic in which the signal intensity increases and decreases according to the periodic characteristic of the single-phase current (e.g., zero crossing point).

[0093] That is, when the insulation between adjacent circuits is damaged or destroyed, or a crack occurs in the circuit due to aging or damage of the circuit, a voltage difference occurs between the points of insulation damage or destruction, or between the two contact points of the circuits that are short-circuited by the crack (hereinafter referred to as arc contacts), and a discharge phenomenon, i.e., an arc, occurs due to the voltage difference that occurs.

[0094] Referring to FIG. 3, the periodic characteristics of the occurrence and extinction of an arc can be examined. The arc may have a periodic characteristic in which the arc does not occur (No Arc stage (No Arcing)) (281, 291) as the voltage difference between the arc contacts is small, the arc strike stage (Arc Strikes) stage (282, 292) in which the arc begins to occur at the arc contacts as the voltage difference between the arc contacts increases, the arc conduct stage (283, 293) in which current is conducted between the arc contacts through the current discharged from the arc contacts as the voltage difference between the arc contacts reaches a maximum value, and the arc quench stage (Arc Quenches) stage (284, 294) in which the arc is extinguished as the voltage between the arc contacts decreases.

[0095] In this case, the intensity of the high-frequency current signal may be different in each of the no-arc phase (281, 291), the arc strike phase (282, 292), the arc conduct phase ((283, 293)), and the arc quench phase (284, 294). For example, the arc strike phase (282, 292) and the arc quench phase (284, 294) may be phases in which the voltage difference between the arc contacts is large and thus the arc is generated at its largest, since the current does not flow despite having a large voltage. In other words, these may be phases in which the high-frequency current signal is generated at its strongest.

[0096] In addition, the arc conduction stage (283, 293) is a stage in which current is conducted between the arc contacts due to an arc discharge, and may be a stage in which the arc is reduced due to current conduction despite having the largest voltage according to the periodic characteristics of the single-phase current. In other words, it may be a stage in which the intensity of the high-frequency noise current signal is reduced. In addition, the no-arc stage (281, 291) is a stage in which the arc does not occur or is extinguished due to a small voltage difference between the arc contacts, and may be a stage in which the intensity of the high-frequency current signal is the weakest because the arc occurs the least.

[0097] Accordingly, a maximum high-frequency current signal may be generated in the arc strike stage (282, 292) and the arc quench stage (284, 294), a signal smaller than the maximum high-frequency current signal may be generated in the arc conduct stage (282, 292), and a weaker high-frequency current signal may be generated in the no-arc stage (281, 291) than the high-frequency current signal generated in the arc conduct stage.

[0098] That is, if the intensity of the high-frequency current signal generated in the no-arc stage (281, 291) is referred to as the first signal intensity, a high-frequency current signal of a second signal intensity stronger than the first signal intensity is generated in the arc conduct stage (283, 293), and a high-frequency current signal of a third signal intensity stronger than the second signal intensity is generated in the arc strike stage (282, 292) and the arc quench stage (284, 294).

[0099] Meanwhile, in the case of insulation breakdown, since the no-arc phase - arc strike phase - arc conduct phase - arc quench phase - no-arc phase are repeated between ZCP (Zero Crossing Point) of the single-phase current, that is, during the half cycle of the single-phase current, the intensity of the high-frequency current signal may also have a change pattern. In addition, the arc monitoring control unit (200-1) can detect whether an arc due to insulation breakdown has occurred in the power line (50) based on the signal intensity change pattern of the high-frequency current signal. Here, the ZCP is a point in time when the polarity is reversed according to the periodic characteristics of the alternating current, and means a point in time when the voltage is 0.

[0100] To this end, the arc monitoring control unit (200-1) can determine a sampling point at which to sample a preset number of high-frequency current signal samples between ZCP and ZCP (half cycle) of the single-phase current. For example, the arc monitoring control unit (200-1) can obtain a preset number of samples from a point corresponding to ZCP.

[0101] In this case, the arc monitoring control unit (200-1) can obtain a preset number of samples (first sample) based on a time point corresponding to a half cycle (ZCP) of the single-phase current. In addition, the preset number of samples (second sample) can be obtained based on a time point corresponding to a 1 / 8 cycle of the single-phase current. In addition, the preset number of samples (third sample) can be obtained based on a time point corresponding to a 2 / 8 cycle (1 / 4 cycle) of the single-phase current, that is, a time point having a maximum voltage. Finally, the preset number of samples (fourth sample) can be obtained again based on a time point corresponding to a 3 / 8 cycle of the single-phase current. It should be understood that the sampling time points described above are merely examples to assist in explaining the present invention, and the present invention is not limited thereto. In addition, the arc monitoring control unit (200-1) can calculate signal intensity averages for each of the preset numbers of acquired samples. Accordingly, the signal average of the first samples (first signal intensity average), the signal average of the second samples (second signal intensity average), the signal average of the third samples, and the signal average of the fourth samples (third signal intensity average and fourth signal intensity average) can be calculated, respectively.

[0102] Here, the first samples may be samples obtained in the no-arc step (281, 291), the second samples may be samples obtained in the arc strike step (282, 292), and the third samples may be samples obtained in the arc conduct step (283, 293), and the fourth samples may be samples obtained in the arc quench step (284, 294).

[0103] Accordingly, the first signal intensity average may be a signal intensity average of samples acquired in the no-arc step (281, 291). And the second signal intensity average may be a signal intensity average of samples acquired in the arc strike step (282, 292), and the third signal intensity average and the fourth signal intensity average may be signal intensity averages of samples acquired in the arc conduct step (283, 293) and the arc quench step (284, 294), respectively.

[0104] Then, the arc monitoring control unit (200-1) can detect the intensity change pattern of the high-frequency current signal from the signal intensity averages of each stage. For example, the arc monitoring control unit (200-1) can detect the change in the signal intensity average when the cycle of the single-phase current progresses from the ZCP point to the 1 / 8 cycle point by comparing the first signal intensity average and the second signal intensity average. And, by comparing the second signal intensity average and the third signal intensity average, the change in the signal intensity average can be detected when the cycle of the single-phase current progresses from the 1 / 8 cycle point to the 2 / 8 cycle point (1 / 4 cycle) point. In the same manner, the third signal average and the fourth signal average can be compared, and the fourth signal average and the first signal average of the next cycle can be compared, to detect the change in the signal intensity average when the cycle of the single-phase current progresses from the 2 / 8 cycle point to the 3 / 8 cycle point, and from the 3 / 8 cycle point to the 4 / 8 cycle point (half cycle, i.e., ZCP).

[0105] If an arc occurs here, the intensity of the high-frequency current signal is the weakest in the no-arc phase (around the ZCP) (281), and then the intensity of the high-frequency current signal may increase as it enters the arc strike phase (282). Then, as it passes the arc strike phase (282) and enters the arc conduct phase (maximum voltage state, 1 / 4 cycle) (283), the current may be conducted, and the intensity of the high-frequency current signal may decrease again. And as it enters the arc quench phase (284) from the arc conduct phase (283), the current conduction is interrupted, and thus the intensity of the high-frequency current signal may increase again, and as it enters the no-arc phase (291), which is the ZCP state, the intensity of the high-frequency current signal may weaken again.

[0106] Therefore, if an arc occurs, the change in the signal intensity average may increase when moving from the first signal average to the second signal average, decrease when moving from the second signal average to the third signal average, increase again when moving from the third signal average to the fourth signal average, and decrease again when moving from the fourth signal average to the first signal average of the next cycle. That is, the change pattern of the signal intensity average may have a pattern of increase - decrease - increase - decrease, and may have a characteristic in which the intensity of the third signal intensity average is greater than that of the first signal intensity average.

[0107] Accordingly, the arc monitoring control unit (200-1) can determine that a pattern corresponding to arc occurrence has been formed when a change pattern and characteristic of the signal intensity average (a characteristic in which the intensity of the third signal intensity average is greater than that of the first signal intensity average) is detected.

[0108] Then, the arc monitoring control unit (200-1) can transmit the result of determining whether an arc has occurred based on the pattern of the high-frequency current signal to the control unit (100) of the blocking unit (10). Then, the control unit (100) can control the semiconductor circuit breaker (110) based on the result of determining whether an arc has occurred, thereby blocking the electrical connection with the power line (50).

[0109] Here, the arc monitoring control unit (200) may, of course, transmit a blocking signal to the control unit (100) to operate the semiconductor circuit breaker (110) only when an arc has occurred as a result of the determination of whether an arc has occurred. Alternatively, the arc monitoring control unit (200) may transmit signal intensity pattern information analyzed by each of the acquired samples, that is, signal intensity pattern information formed in the first to third steps, to the control unit (100), and the control unit (100) may, of course, determine whether an arc has occurred based on the received signal intensity pattern information.

[0110] Meanwhile, the arc monitoring control unit (200-1) or the control unit (100) may, of course, determine whether an arc has occurred based on whether a change pattern of the signal intensity average corresponding to the arc occurrence pattern is detected a preset number of times over a certain period of time in order to more accurately determine whether an arc has occurred. In this case, if a change pattern of the signal intensity average corresponding to the arc pattern is detected a preset number of times over a certain period of time, the arc monitoring control unit (200-1) or the control unit (100) may determine that an arc has occurred.

[0111] Meanwhile, the above Fig. 2a illustrates an example in which a single-phase current, i.e., an alternating current, flows through the power line (50). However, in the case in which a direct current flows through the power line (50), the direct current does not have a ZCP, so it may be difficult to determine whether an arc has occurred using the method described in the above Fig. 2a.

[0112] Accordingly, when the current flowing in the power line (50) is a direct current, it is possible to determine whether an arc has occurred from the power line (50) by using an arc monitoring unit (20) having a different configuration from the arc monitoring unit (20) illustrated in FIG. 2a. Hereinafter, referring to FIG. 3, the configuration of the arc monitoring unit (200-2) that monitors the occurrence of an arc from a power line (50) through which a direct current flows will be examined in FIG. 3.

[0113] Referring to FIG. 3, the arc monitoring unit (20) of the insulation monitoring system (1) according to an embodiment of the present invention may be configured to include an HFCT (210), a filter unit (220), an FFT (Fast Fourier Transformer) (260), an arc monitoring control unit (200-2), and a memory (270) connected to the arc monitoring control unit (200-2).

[0114] Here, the HFCT (210) can detect a high-frequency current signal resulting from partial discharge occurring in a power line (50) as described above.

[0115] And the filter unit (220) is a filter that filters a specific frequency using a frequency mask method, and as described above, it can be a filter for removing noise whose frequency band is known in advance, such as living noise, load driving noise, or electromagnetic noise. Therefore, a high-frequency current signal of a power line (50) from which noise, such as living noise or load driving noise, is removed can be obtained through the HFCT (210) and the filter unit (220).

[0116] Meanwhile, the FFT (260) can perform a fast Fourier transform on the high-frequency current signal of the power line (50) from which the noise has been removed. Accordingly, the acquired high-frequency current signal can be decomposed into the size of each frequency component. In this case, if an arc does not occur in the power line (50), there may be no high-frequency current signal detected by the HFCT (210), and thus the calculation result of the FFT (260) may produce a value of 0. Then, the arc monitoring control unit (200-2) that receives the calculation result of the FFT (260) can determine that there is no arc discharge.

[0117] However, even if an arc occurs in the power line (50) or no arc occurs, various noises may occur due to arbitrary environmental factors. For example, a temporary change in the electric field may occur due to a temporary change in the magnetic field formed nearby, such as due to lightning, and a high-frequency current signal may be generated in the power line (50) due to this change in the electric field. In addition, the generated high-frequency current signal may be detected through the HFCT (210) and the filter unit (220) and applied to the FFT (260). Then, the FFT (260) can decompose the input high-frequency current signal into frequency components and calculate the size of each frequency component.

[0118] Then, the arc monitoring control unit (200-2) can determine whether an arc has occurred in the power line (50) from the magnitude of each frequency component of the high-frequency current signal input from the FFT (260). For example, the arc monitoring control unit (200-2) can detect whether, among the magnitudes of each frequency component, there are magnitudes corresponding to at least one frequency component that mainly occurs when an arc occurs. If at least one frequency component that mainly occurs when an arc occurs is included in the high-frequency current signal, the magnitudes of the detected frequency components can be added. If the added magnitude is greater than a preset reference value, it can be determined that an arc has occurred. Here, information on at least one frequency component that mainly occurs when an arc occurs can be stored in the memory (270).

[0119] That is, the memory (270) contains information on at least one frequency band related to the occurrence of an arc, and the arc monitoring control unit (200-2) can detect a frequency component corresponding to at least one frequency band stored in the memory (270) among each frequency component included in the high-frequency current signal in the calculation result of the FFT (260). And, based on the result of comparing the sum of the sizes of the detected frequency components with a preset reference value, it is possible to determine whether an arc has occurred.

[0120] Meanwhile, as described above, when an AC current flows in the power line (50), the arc monitoring unit (20) can have the configuration illustrated in FIG. 2a, and when a DC current flows in the power line (50), the arc monitoring unit (20) can have the configuration illustrated in FIG. 3. Although the arc monitoring unit (20) has been described by dividing it into FIG. 2a and FIG. 3, it is to be understood that the arc monitoring unit (20) may be configured as a single unit. For example, the arc monitoring control unit can perform both the function of the arc monitoring control unit (200-1) and the function of the arc monitoring control unit (200-2). In addition, by further providing the FFT (260) and the memory (270) described in FIG. 3 to the configuration of FIG. 2a, it may be configured to enable detection of both a DC arc and an AC arc.

[0121] Accordingly, in the following description, for the convenience of explanation, the arc monitoring control unit (200-1) that can determine whether an arc occurs in a power line (50) for an alternating current and the arc monitoring control unit (200-2) that can determine whether an arc occurs in a power line (50) for a direct current are collectively referred to as the arc monitoring control unit (200).

[0122] Meanwhile, FIG. 4 is a block diagram showing the configuration of an insulation monitoring unit (30) of an insulation monitoring system (1) according to an embodiment of the present invention.

[0123] Referring to FIG. 4, the insulation monitoring unit (30) of the insulation monitoring system (1) according to an embodiment of the present invention includes a coupler resistor (Rc, 370) connected to power lines of a system (hereinafter, power lines, 50), a signal generating unit (330) that applies a pulse signal in the form of a square wave to the power line (50) through the coupler resistor (370), a virtual insulation resistance (Re, 340) formed between the power line (50) and the ground, a signal measuring unit (320) including a detection resistor (Rm) connected to the ground, an ADC (Analog Digital Converter) (302) connected to the signal measuring unit (320) that converts the voltage measured by the signal measuring unit (320) into a digital value, an average voltage calculating unit (310) that receives the digital value converted by the ADC (302) and calculates an average voltage according to the pulse signal applied to the power line (50) during a preset sampling period, and controls other connected components, and It may be configured to include an insulation monitoring control unit (300) that detects a plurality of steady-state voltages according to the applied pulse signal based on a plurality of average voltages produced by the production unit (310), and an insulation resistance calculation unit (308) that calculates the size of the insulation resistance (340) based on a plurality of steady-state voltages detected by the insulation monitoring control unit (300). In addition, it may be configured to include a memory (306) in which various data input to the insulation monitoring control unit (300) or output from the insulation monitoring control unit (300) are stored.

[0124] First, the signal generation unit (330) can generate a pulse signal having a constant positive (+) voltage or a constant negative (-) voltage under the control of the insulation monitoring control unit (300). Then, the generated pulse signal can be applied to the power line (50). Accordingly, a pulse signal in which positive and negative voltages alternate under the control of the insulation monitoring control unit (300) can be applied to the power line (50).

[0125] Meanwhile, the power line (50) and the ground may be connected to each other through a virtual circuit. A virtual insulation resistance (Re, 340) may be formed between the power line (50) and the ground. In addition, a virtual capacitor (Ce, 350) may be further formed between the power line (50) and the ground. The capacitor (350), together with the insulation resistance (340), may form an insulation impedance (360) between the power line (50) and the ground.

[0126] Accordingly, the pulse signal applied to the power line (50) can be input to the signal measurement unit (320) through the circuit formed between the power line (50) and the ground. Here, the signal measurement unit (320) can detect the voltage of the virtual circuit in which the insulation impedance (360) is reflected based on the voltage across the detection resistor (Rm). The detection result of the signal measurement unit (320) can be amplified through an amplifier (Amp, Amplifier) ​​and converted into a digital value through an ADC (302). Then, it can be input to the insulation monitoring control unit (300).

[0127] And, when the voltage of the virtual circuit for pulse signals of different polarities is calculated, the insulation monitoring control unit (300) can control the insulation resistance calculation unit (308) so that the insulation resistance is calculated based on the virtual circuit voltage of different polarities.

[0128] However, if the voltage changes from positive voltage to negative voltage or the polarity of the pulse signal changes from negative voltage to positive voltage, discharge and charge by the insulating capacitor (350) may be induced. Accordingly, a transient period occurs in which the voltage increases by several times more than the applied pulse voltage, and the virtual circuit voltage becomes unstable. In this case, when the voltage of the virtual circuit is unstable, an accurate insulation resistance is not calculated, and therefore, the insulation monitoring control unit (300) can determine a sampling interval and determine whether the virtual circuit voltage is stabilized based on a change in the virtual circuit voltage measured by the signal measurement unit (320) according to the determined sampling interval.

[0129] To this end, the insulation monitoring control unit (300) can detect the voltage of the virtual circuit at each sampling interval. Then, the average voltage calculation unit (310) can be controlled to calculate the average voltage of the virtual circuit during the sampling period according to the sampling interval. Then, when the calculated average voltage is less than or equal to a preset error value, it can be determined that the virtual circuit voltage is stabilized. Then, the insulation monitoring control unit (300) can control the insulation resistance calculation unit (308) to calculate the size of the insulation resistance (340) based on the virtual circuit voltage (first average voltage) in a stabilized state calculated before the polarity of the pulse signal is inverted and the virtual circuit voltage (second average voltage) in a stabilized state calculated after the polarity of the pulse signal is inverted. That is, the size of the insulation resistance (340) can be calculated after the virtual circuit voltage is stabilized. And the insulation monitoring unit (30) can control the signal generation unit (330) so that the polarity of the pulse signal is reversed and perform the same process again to continuously calculate the size of the insulation resistance (340).

[0130] Meanwhile, if the insulation state of the power line (50) is broken, the size of the insulation resistance (340) of the virtual circuit may decrease. On the other hand, if the insulation state of the power line (50) is maintained, the insulation resistance (340) of the virtual circuit may have a sufficient size. Accordingly, the insulation monitoring control unit (300) can determine the insulation state of the power line (50) based on the size of the calculated insulation resistance (340).

[0131] The insulation monitoring control unit (300) above can compare the insulation resistance size with a preset reference value when the insulation resistance is calculated. Then, the insulation status of the power line (50) can be determined based on the comparison result. Then, when the insulation is determined to be in a broken state, the control unit (100) of the blocking unit (10) can be requested to drive the semiconductor circuit breaker (110). Then, the control unit (100) of the blocking unit (10) can output a blocking control signal to the semiconductor circuit breaker (110) to block the electrical connection with the power line (50).

[0132] Alternatively, the insulation monitoring control unit (300) may transmit the calculated insulation resistance to the control unit (100) of the blocking unit (10). Then, the control unit (100) may compare the received insulation resistance with a reference value to determine the insulation state of the power line (50), and may operate the semiconductor circuit breaker (110) according to the determined insulation state.

[0133] Meanwhile, the insulation monitoring unit (30) can also determine the insulation status of the power line (50) for not only direct current but also alternating current. For example, in the case of alternating current, the insulation monitoring unit (30) may further include a converter (not shown) for converting the alternating current of the power line (50) into direct current. In this case, a pulse signal can be applied to the power line (50) through which the alternating current flows through the converter, and the alternating current detected from the power line (50) can be converted into direct current through the converter. In addition, the signal measuring unit (320) can detect the voltage of the converted direct current. Accordingly, the insulation monitoring unit (30) can monitor the insulation status of not only the power line through which the direct current flows but also the power line through which the alternating current flows.

[0134] Figure 5 is a block diagram showing the configuration of a blocking unit (10) of an insulation monitoring system (1) according to an embodiment of the present invention.

[0135] As shown in Fig. 5, the blocking unit (10) may include a semiconductor circuit breaker (110) composed of a plurality of semiconductor switches (112-1, 112-2) connected in series to connect a bidirectional current flow. Here, the semiconductor circuit breaker (110) may be a solid state circuit breaker (SSCB) capable of high-speed current blocking.

[0136] First, the first semiconductor switch (112-1) may be a semiconductor switch having a source terminal connected to one end (A side) of the semiconductor circuit breaker (110) and a drain terminal connected to the other end (B side). In addition, the drain terminal and the source terminal may be connected through a diode (a first diode (113-1)) in which a positive (+) pole is connected to the drain terminal and a negative (-) pole is connected to the source terminal. In addition, the second semiconductor switch (112-2) may be a semiconductor switch having a source terminal connected to the other end (B side) of the semiconductor circuit breaker (110) and a drain terminal connected to one end (A side). In addition, the drain terminal and the source terminal may be connected through a diode (a first diode (113-2)) in which a positive (+) pole is connected to the drain terminal and a negative (-) pole is connected to the source terminal. In this way, by connecting a plurality of semiconductor switches in series, each of which has a source terminal and a drain terminal connected to different ends of the semiconductor circuit breaker, the semiconductor circuit breaker (110) can be formed to control the flow of bidirectional current flowing from the B side to the A side as well as the current flowing from the A side to the B side.

[0137] Meanwhile, the source terminal and the drain terminal of each of the first semiconductor switch (112-1) and the second semiconductor switch (112-2) may be connected through the gate terminal of each semiconductor switch. Each gate terminal is connected to each gate driver (111-1, 111-2), and the source terminal and the drain terminal may be electrically connected based on the voltage applied to the gate terminal from the gate driver, i.e., the gate voltage. In this case, when the gate voltage is higher than a preset threshold voltage, the source terminal and the drain terminal may be electrically connected. On the other hand, when the gate voltage is lower than the threshold voltage or the gate voltage is not applied, the source terminal and the drain terminal may not be electrically connected. That is, the electrical connection between the A side and the B side may be cut off.

[0138] Meanwhile, the blocking unit (10) may further include a blocking switch (MCCB, Molded Case Circuit Breaker) (130) to physically block the electrical connection between the A side and the B side in addition to the electrical blocking using the semiconductor circuit breaker (110). In this case, the semiconductor circuit breaker (110) primarily blocks the electrical connection between the A side and the B side, and when the electrical connection between the A side and the B side is blocked by the semiconductor circuit breaker (110), the blocking switch (150) physically blocks the connection between the A side and the B side, thereby more safely blocking the connection between the power source and the load where an error has occurred.

[0139] Meanwhile, the blocking unit (10) may be equipped with a control unit (100) for controlling the semiconductor circuit breaker (110). In addition, it may include a memory (120) in which data and commands supporting the operation of the control unit (100) are stored.

[0140] The above control unit (100) controls the gate driver (111-1, 111-2) of the semiconductor circuit breaker (110) to control the gate voltage applied to the gate terminal of each semiconductor switch (112-1, 112-2), thereby controlling the semiconductor circuit breaker (110) so that the electrical connection between the A side and the B side is cut off.

[0141] Here, the control unit (100) can control the semiconductor circuit breaker (110) based on the arc monitoring result received from the arc monitoring control unit (200) or the insulation status monitoring result received from the insulation monitoring control unit (200). In this case, the arc monitoring result may be whether an arc has occurred in the power line (50) as determined by the arc monitoring unit (20). In addition, the insulation monitoring result may be whether an insulation breakdown has occurred in the power line (50) as determined by the insulation monitoring unit (30).

[0142] Alternatively, the control unit (100) may receive signal intensity change pattern information of a high-frequency current signal as an arc monitoring result of the arc monitoring unit (20) or may receive the summed size of frequency components related to the arc. Then, the received signal intensity change pattern information may be compared with pre-stored pattern information or the summed size may be compared with a preset reference size to determine whether an arc has occurred. Then, the control unit (100) may receive insulation resistance as an insulation monitoring result from the insulation monitoring unit (30) and compare the received insulation resistance with a reference value to determine the insulation status of the power line (50). Then, the semiconductor circuit breaker (110) may be driven according to the determination result.

[0143] Meanwhile, the description of Fig. 5 described above illustrates an example in which two semiconductor switches (111-1, 111-2) are connected in series so that a bidirectional current flow can be formed. However, if the power line (50) is a unidirectional circuit in which current flows in one direction, it goes without saying that only one semiconductor switch may be provided.

[0144] In the above description, the configuration of an insulation monitoring system (1) according to an embodiment of the present invention has been described.

[0145] In the following description, the operation process of the insulation monitoring system (1) according to the embodiment of the present invention described above will be examined in more detail with reference to a plurality of flowcharts.

[0146] First, FIGS. 6 and 7 illustrate different operation processes of an insulation monitoring system (1) that monitors whether an arc occurs and whether insulation breakdown occurs from a power line (50) when an AC current flows through the power line. In this case, the insulation monitoring unit (30) may further include a converter (not shown) that converts the AC current of the power line (50) into a DC current or converts the DC current into an AC current. In addition, a pulse signal can be applied to the power line (50) through which the AC current flows through the converter, and the AC current detected from the power line (50) can be converted into a DC current through the converter.

[0147] First, FIG. 6 is a flowchart illustrating an operation process in which an arc monitoring unit (20), an insulation monitoring unit (30), and a blocking unit (10) are linked in an insulation monitoring system (1) according to an embodiment of the present invention.

[0148] Referring to FIG. 6, the arc monitoring control unit (200) and the insulation monitoring control unit (300) can operate separately from each other to monitor the insulation status of the power line (50). Accordingly, the monitoring operation of the arc monitoring control unit (200) and the monitoring operation of the insulation monitoring control unit (300) can be performed simultaneously and in parallel.

[0149] First, looking at the operation process of the arc monitoring control unit (200), the arc monitoring control unit (200) can first obtain samples of a high-frequency current signal (S610). Here, the samples of the high-frequency current signal may be samples detected based on a plurality of time points determined according to the cycle of the AC current from the intensity of the high-frequency current signal from which noise components have been filtered. For example, in step S610, the arc monitoring control unit (200) can obtain a preset number of high-frequency current signal intensity samples based on each time point, respectively, at each time point corresponding to the ZCP of the AC current, that is, a half-cycle (time point 1), a 1 / 8 cycle (time point 2), a 1 / 4 cycle (time point 3), and a 3 / 8 cycle (time point 4). In addition, the arc monitoring control unit (200) can average the obtained samples for each time point at which sampling is performed, and calculate average signal intensities for each time point (S612).

[0150] And the arc monitoring control unit (200) can detect the intensity change pattern of the high-frequency current signal based on the calculated average signal intensities for each time point (S614). In the step S614, the arc monitoring control unit (200) can compare the average signal intensity of the first time point with the average signal intensity of the second time point, and compare the average signal intensity of the second time point with the average signal intensity of the third time point. And the average signal intensity of the third time point can be compared with the average signal intensity of the fourth time point, and compare the average signal intensity of the fourth time point with the average signal intensity of the first time point of the next cycle. And the average signal intensity of the first time point can be compared with the average signal intensity of the third time point. The result of this signal intensity comparison may be the signal intensity change pattern.

[0151] Then, the arc monitoring control unit (200) can determine whether the detected signal intensity change pattern matches a preset pattern, i.e., a pattern corresponding to arc occurrence (hereinafter referred to as an arc pattern) (S616). For example, the arc pattern may be a pattern in which the signal intensity change pattern from the first time point to the fourth time point repeats increase-decrease-increase-decrease, i.e., increase and then decrease, and the average signal intensity at the third time point has a greater value than the average signal intensity at the first time point.

[0152] As a result of the determination in step S616, if the signal intensity change pattern detected in step S614 does not match the arc pattern, the arc monitoring control unit (200) can proceed to step S610 again. Then, the following process can be performed again to monitor whether an arc has occurred.

[0153] However, if the signal intensity change pattern detected in the step S614 matches the arc pattern as a result of the determination in the step S616, the arc monitoring control unit (200) can determine that an arc has occurred in the power line (50). Then, the arc monitoring control unit (200) can transmit an insulation abnormality signal to the control unit (100) of the blocking unit (10) (S618). Then, the control unit (100) of the blocking unit (10) can output a blocking signal to the semiconductor circuit breaker (110) to block the connection with the power line (50) (S630). In this case, the blocking signal may include a blocking switch control signal that drives the blocking switch (150) to physically block the power line (50).

[0154] Meanwhile, the control unit (100) of the above-described blocking unit (10) can output a drive stop signal to the insulation monitoring control unit (300) when the load is cut off from the power line (50) according to the blocking signal (S631). Then, the insulation monitoring control unit (300) can stop the insulation monitoring operation. Similarly, the control unit (100) of the above-described blocking unit (10) can output a drive stop signal to the arc monitoring control unit (200) to prevent unnecessary arc monitoring operations from being performed.

[0155] Meanwhile, the step S616 may further include a step of repeating the steps S610 to S614 a preset number of times or more. In this case, if a signal intensity change pattern matching the arc pattern is detected, the arc monitoring control unit (200) may perform the steps S610 to S614 again. In addition, if a signal intensity change pattern matching the arc pattern is detected a preset number of times over a certain period of time as a result of repeating the steps S610 to S614, it may be determined that an arc has occurred in the power line (50).

[0156] Meanwhile, separately from the arc monitoring performed by the arc monitoring control unit (200), the insulation monitoring control unit (300) can perform insulation monitoring. Therefore, the insulation monitoring can be performed while the arc monitoring is being performed.

[0157] First, the insulation monitoring control unit (300) can apply a square wave pulse signal with reversed polarity to the power line (50) (S620). Then, it can check whether a preset initial waiting time has elapsed to detect whether the voltage is stabilized (S621). If the initial waiting time has elapsed, the virtual circuit voltage detected by the signal measuring unit (320) can be detected as the initial value (S622).

[0158] And the insulation monitoring control unit (300) can acquire the next sample according to the preset sampling interval (S623). Here, the acquired sample may be a virtual circuit voltage calculated after the sampling interval has elapsed. And, the average voltage between the acquired samples can be calculated (S624). In this case, the average voltage between the initial value and the next sample (the first sample) can be calculated.

[0159] Meanwhile, once the average voltage is calculated, the insulation monitoring control unit (300) can determine whether the voltage difference between the previously calculated average voltage and the currently calculated average voltage is within a preset error range (S625). In this case, since there is no previously calculated average voltage, the voltage difference between the average voltages may fall outside the preset error range. Then, the insulation monitoring control unit (300) can proceed to step S623 again to acquire the next sample (second sample) according to the sampling interval.

[0160] Then, in step S624, the average voltage between the first sample and the second sample can be calculated. Then, the control unit (100) can compare the currently calculated average voltage with the previously calculated average voltage (average voltage between the initial value and the first sample) to determine whether the voltage difference is within a preset normal range. If it is out of the normal range, the process can proceed to step S623 again, and the process from step S623 to step S625 can be repeated.

[0161] Meanwhile, if the voltage difference between the average voltages is within the preset error range as a result of the determination at step S625, the insulation monitoring control unit (300) determines that the transient period due to the polarity inversion of the pulse signal has passed, and can determine the currently detected voltage as a voltage in a stable state, i.e., a normal voltage. Then, the insulation monitoring control unit (300) can calculate the insulation resistance based on the normal voltage determined before the polarity inversion of the pulse signal and the currently determined normal voltage, i.e., the normal voltages determined when the polarities of the pulse signal are different (S626).

[0162] And the insulation monitoring control unit (300) can compare the size of the calculated insulation resistance with a preset reference value (S627). As a result of the determination in step S627, if the insulation resistance calculated in step S626 is equal to or higher than the preset reference value, the insulation monitoring control unit (300) can determine that the insulation condition of the power line (50) is good. Then, the insulation monitoring control unit (300) can proceed to step S620 again and perform the following process again.

[0163] However, if the insulation resistance calculated in step S626 is less than the preset reference value as a result of the determination in step S627, the insulation monitoring control unit (300) may determine that the insulation of the power line (50) has been broken. Then, the insulation monitoring control unit (300) may transmit an insulation abnormality signal to the control unit (100) of the blocking unit (10) (S628). Then, the control unit (100) of the blocking unit (10) may output a blocking signal to the semiconductor circuit breaker (110) to block the connection with the power line (50) (S630). In this case, the blocking signal may include a blocking switch control signal that drives the blocking switch (150) to physically block the power line (50).

[0164] Meanwhile, the control unit (100) of the above-described blocking unit (10) can output an operation stop signal to the arc monitoring control unit (200) when the load is cut off from the power line (50) according to the blocking signal (S631). Then, the arc monitoring control unit (200) can stop the arc monitoring operation. Similarly, the control unit (100) of the above-described blocking unit (10) can output an operation stop signal to the insulation monitoring control unit (300) to prevent unnecessary operations from being performed.

[0165] Meanwhile, in the above description, it was explained as an example that the blocking from the power line (50) is performed based on either the arc monitoring result of the arc monitoring control unit (200) or the insulation monitoring result of the insulation monitoring control unit (300), but it is of course possible for the control unit (100) of the blocking unit (10) to control the semiconductor circuit breaker (110) so that the blocking operation is performed based on both the arc monitoring result and the insulation monitoring result.

[0166] For example, when an insulation abnormality signal is received from the arc monitoring control unit (200) (step S618), the control unit (100) can postpone the blocking operation until the insulation monitoring result is received from the insulation monitoring control unit (300). In addition, when the insulation abnormality signal is also received from the insulation monitoring control unit (300) (step S628), the control unit (100) can perform the blocking operation. Or, conversely, when an insulation abnormality signal is received from the insulation monitoring control unit (300) (step S628), the control unit (100) can postpone the blocking operation until the insulation monitoring result is received from the arc monitoring control unit (200), and when the insulation abnormality signal is also received from the arc monitoring control unit (200) (step S618), the control unit can perform the blocking operation. In other words, by operating the arc monitoring result and the insulation monitoring result complementarily, the reliability of insulation breakdown detection can be further improved.

[0167] Meanwhile, in the above description, it was explained as an example that arc monitoring and insulation monitoring are performed separately, but it is of course possible that arc monitoring may be performed to monitor the insulation status of the power line (50) while insulation monitoring is not performed.

[0168] As described above, in the case of insulation monitoring performed through insulation resistance in the insulation monitoring unit (30) as described above, a virtual circuit voltage is required in a state where pulse voltages with different polarities are applied in order to calculate the insulation resistance. However, since the virtual circuit including the insulation resistance includes not only the insulation resistance but also an insulating capacitor, when the polarity of the pulse voltage is reversed, discharge and charge occur according to the insulating capacitor, and this causes a transient period in which the voltage is unstable, unlike the applied pulse voltage. Therefore, the insulation monitoring control unit (300) has a problem in that there is a time period in which the insulation resistance is not calculated from the time the polarity of the pulse signal is reversed until the transient period has elapsed, and during that time, the insulation status of the power line cannot be monitored.

[0169] Accordingly, the insulation monitoring system (1) according to an embodiment of the present invention monitors the insulation status of the power line (50) by determining whether an arc has occurred in the power line (50) based on the detection result of the arc monitoring unit (20) during a time when the insulation monitoring unit (30) cannot calculate the insulation resistance, and when the insulation resistance is calculated, the insulation status of the power line (50) can be monitored based on the insulation resistance.

[0170] FIG. 7 is a flowchart illustrating the operation process of a blocking unit (10) that performs insulation monitoring on a power line (50) by linking the arc monitoring unit (20) and the insulation monitoring unit (30) based on the voltage stabilization period according to the polarity reversal of the pulse signal in the insulation monitoring unit (30) as an example of an insulation monitoring system (1) according to an embodiment of the present invention in such a case.

[0171] Meanwhile, according to the above-described explanation, it has been mentioned that the arc monitoring unit (20) does not directly determine whether an arc has occurred, but provides the signal intensity change pattern of the detected high-frequency current signal to the blocking unit (10), so that the blocking unit (10) can determine whether an arc has occurred. In addition, it has been mentioned that the insulation monitoring unit (30) does not directly determine the insulation status of the power line (50), but provides the calculated insulation resistance to the blocking unit (10), so that the blocking unit (10) can determine the insulation status of the power line (50). The blocking unit (10) of FIG. 7 below receives the signal intensity change pattern of the high-frequency current signal and the calculated insulation resistance, so that the blocking unit (10) can directly determine the insulation status of the power line (50), as an example.

[0172] Referring to Fig. 7, the control unit (100) of the blocking unit (10) can first detect whether the polarity of the pulse signal in the insulation monitoring unit (30) has been reversed (S700).

[0173] For example, when the polarity of the pulse signal is reversed in the insulation monitoring unit (30), the control unit (100) can receive a notification signal (pulse polarity reverse signal) from the insulation monitoring unit (30) that notifies the polarity of the pulse signal.

[0174] To this end, step S620 of the above-described FIG. 6 may further include a step in which, when a polarity inversion of a pulse signal occurs, the insulation monitoring control unit (300) transmits the notification signal to the control unit (100). In this case, step S700 may be a step in which a pulse signal polarity inversion signal is received from the insulation monitoring unit (30).

[0175] If the detection result of the above step S700 is that the polarity of the pulse signal has been inverted, the control unit (100) can check whether the insulation monitoring unit (30) has entered the voltage stabilization phase (S702). Here, the voltage stabilization phase may be a phase in which the insulation resistance can be calculated as a transition period following the polarity inversion of the pulse signal has passed. Therefore, the control unit (100) can check whether the insulation monitoring unit (30) has entered the voltage stabilization state based on whether the insulation resistance has been received from the insulation monitoring unit (30) after the notification signal notifying the polarity inversion of the pulse signal has been received (S702).

[0176] If the insulation monitoring unit (30) fails to enter the voltage stabilization state as a result of the check at step S702, the control unit (100) can receive signal intensity change pattern information of the high-frequency current signal detected from the arc monitoring unit (20) (S704). For example, the signal intensity change pattern information can be detected for each half cycle of the current flowing in the power line (50), for example, the alternating current.

[0177] Then, the control unit (100) can determine whether the received signal intensity change pattern matches a preset arc pattern (S706). Here, information on the arc pattern can be stored in the memory (120) of the blocking unit (10).

[0178] As a result of the determination in step S706, if the signal intensity change pattern received from the arc monitoring unit (20) matches the pre-stored arc pattern, the control unit (100) can output a blocking signal for the semiconductor circuit breaker (110) to block the load from the power line (50) even though the insulation resistance is not received from the insulation monitoring unit (30) (S708). In addition, in order to prevent unnecessary operation of the insulation monitoring unit (30), an operation stop signal can be transmitted to the insulation monitoring unit (30) (S710). Similarly, the control unit (100) can transmit an operation stop signal to the arc monitoring unit (20).

[0179] Meanwhile, if the determination result of step S706 shows that the signal intensity change pattern received from the arc monitoring unit (20) does not match the previously stored arc pattern, the control unit (100) can proceed to step S702 again to check whether the insulation monitoring unit (30) has entered the voltage stabilization state. If the check result of step S702 shows that the insulation monitoring unit (30) has not entered the voltage stabilization state, the process from step S704 to step S706 can be performed again. That is, insulation monitoring according to the detection result of the arc monitoring unit (20) can be continuously performed until the insulation resistance is received from the insulation monitoring unit (30).

[0180] On the other hand, if the insulation monitoring unit (30) has entered the voltage stabilization state as a result of the check at step S702, that is, if the insulation resistance is received from the insulation monitoring unit (30), the control unit (100) can compare the received insulation resistance with the reference value previously stored in the memory (120) (S712). And if the comparison result at step S712 shows that the insulation resistance is lower than the reference value, the semiconductor circuit breaker (110) can output a blocking signal to block the load from the power line (50) (S714). And, in order to prevent unnecessary operation of the arc monitoring unit (20), an operation stop signal can be transmitted to the arc monitoring unit (20) (S716). Similarly, the control unit (100) can transmit an operation stop signal to the insulation monitoring unit (30).

[0181] However, if the insulation resistance is higher than the reference value as a result of the comparison at step S712, it can be determined that the insulation condition of the power line (50) is good. Therefore, the blocking unit (10) can proceed to step S700 again to check whether the pulse signal polarity reversal notification signal received from the insulation monitoring unit (30) has been received.

[0182] Then, when the insulation monitoring unit (30) reverses the polarity of the pulse signal to calculate the next insulation resistance, the pulse signal polarity reverse notification signal is received by the blocking unit (10) again, and the process proceeds from step S700 to step S702, so that the insulation status of the power line (50) can be monitored through arc monitoring until the insulation monitoring unit (30) enters the voltage stabilization state according to the polarity reverse of the pulse signal, and through insulation monitoring after the insulation monitoring unit (30) enters the voltage stabilization state.

[0183] Fig. 8 is an exemplary diagram showing an example of insulation monitoring according to whether an arc occurs and insulation resistance based on the voltage stabilization period according to the operation process of Fig. 7.

[0184] Referring to FIG. 8, FIG. 8 illustrates an example of insulation monitoring according to an embodiment of the present invention, a detection time (800) from the point in time when the polarity of the pulse signal is reversed to the point in time when the polarity of the pulse signal is reversed again.

[0185] First, when pulse inversion occurs, the insulation monitoring unit (30) detects the initial value after the initial waiting time (tn) has elapsed, and performs sampling at preset time intervals (t) thereafter. Then, the average voltage of the sampled virtual circuit voltage is calculated at each sampling interval (t), and the difference with the previously calculated average voltage is calculated to determine whether a transient period has elapsed. Then, the insulation resistance can be calculated based on the voltage detected after the transient period has elapsed.

[0186] Therefore, the insulation monitoring system (1) according to an embodiment of the present invention can monitor the insulation status of the power line (50) based on the signal intensity change pattern received from the arc monitoring unit (20), as described in FIG. 7. And, when the voltage reaches a point in time (Tk) where it is stabilized, the insulation status of the power line (50) can be monitored based on the insulation resistance calculated by the insulation monitoring unit (30). That is, during the first period (810) during the detection period (800) when the insulation status cannot be monitored by the insulation monitoring unit (30) due to voltage instability caused by polarity inversion of the pulse signal, the insulation status of the power line (50) can be monitored using the intensity change pattern of the high-frequency current signal of the arc monitoring unit (20), and during the second period (820) when the insulation resistance can be calculated by the insulation monitoring unit (30) as the voltage becomes stabilized, the insulation resistance can be monitored using the insulation resistance calculated by the insulation monitoring unit (30). This can prevent the occurrence of a blank period where insulation monitoring is not performed.

[0187] Meanwhile, the above-described FIGS. 6 to 8 illustrate examples of cases where an alternating current flows through a power line (50). However, it goes without saying that the present invention can be applied not only to power lines where an alternating current flows but also to power lines where a direct current flows. In the case of a power line where a direct current flows, the insulation monitoring unit (30) can directly apply a pulse signal to the power line without a converter, and the signal measuring unit (320) can directly measure the voltage of the power line.

[0188] However, in the case of the arc monitoring unit (20), since the polarity of the direct current is not reversed, it may be difficult to detect the arc based on the cycle according to the ZCP. Accordingly, instead of detecting the change pattern of the high-frequency current signal intensity, the arc monitoring unit (20) performs a fast Fourier transform (FFT) on the detected high-frequency current signal, and detects frequency components occurring when an arc occurs from the fast Fourier transform result, and can monitor the insulation status of the power line through which the direct current flows based on the magnitude of the detected frequency components.

[0189] The following Figures 9 and 10 illustrate different operation processes of an insulation monitoring system (1) that monitors whether an arc occurs and whether insulation is broken from a power line (50) when a direct current flows through the power line.

[0190] First, FIG. 9 is a flowchart illustrating an operation process of an insulation monitoring system (1) according to an embodiment of the present invention for monitoring an insulation status of a power line through which a direct current flows, in which an arc monitoring unit, an insulation monitoring unit, and a cutoff unit are linked together.

[0191] Referring to FIG. 9, the arc monitoring control unit (200) and the insulation monitoring control unit (300) can operate separately from each other to monitor the insulation status of the power line (50). Accordingly, the monitoring operation of the arc monitoring control unit (200) and the monitoring operation of the insulation monitoring control unit (300) can be performed simultaneously and in parallel.

[0192] First, looking at the operation process of the arc monitoring control unit (200), the arc monitoring control unit (200) can obtain a high-frequency current signal with noise removed through the HFCT (210) and the filter unit (220) (S910). Then, the arc monitoring control unit (200) can perform a fast Fourier transform on the obtained high-frequency current signal to decompose the high-frequency current signal into each frequency component (S912).

[0193] And the arc monitoring control unit (200) can detect frequency components corresponding to at least one preset frequency band among the frequency components of the decomposed high-frequency current signal (S914). Here, the at least one preset frequency band may be a frequency band of a high-frequency current signal generated when an arc occurs in a DC circuit. That is, the at least one preset frequency band is a frequency band related to arc occurrence, and may be obtained through statistical data investigated in advance or a plurality of arc occurrence experiments conducted in relation to the present invention. Information on the frequency band related to arc occurrence may be stored in advance in the memory (120), and may be downloaded or updated through wireless communication or wired communication.

[0194] If frequency components of a high-frequency current signal detected by the fast Fourier transform in step S914 are detected and included in at least one arc occurrence-related frequency band stored in the memory (270), the arc monitoring control unit (200) can add up the magnitudes (signal magnitudes) of each of the detected frequency components (S915). Then, the added signal magnitude can be compared with a preset reference magnitude (S916).

[0195] And if the signal size added in step S916 is less than the preset reference size, the arc monitoring control unit (200) can determine that no arc has occurred. Then, the process proceeds to step S910 again, and the subsequent steps can be performed again.

[0196] However, if the determination result of the step S916 is less than the preset standard size, the arc monitoring control unit (200) can determine that an arc has occurred in the power line (50). Then, the arc monitoring control unit (200) can transmit an insulation abnormality signal to the control unit (100) of the blocking unit (10) (S918). Then, the control unit (100) of the blocking unit (10) can output a blocking signal to the semiconductor circuit breaker (110) to block the connection with the power line (50) (S930). In this case, the blocking signal may include a blocking switch control signal that drives the blocking switch (150) to physically block the power line (50).

[0197] Meanwhile, the control unit (100) of the above-described blocking unit (10) can output a drive stop signal to the insulation monitoring control unit (300) when the load is cut off from the power line (50) according to the blocking signal (S931). Then, the insulation monitoring control unit (300) can stop the insulation monitoring operation. Similarly, the control unit (100) of the above-described blocking unit (10) can output a drive stop signal to the arc monitoring control unit (200) to prevent unnecessary arc monitoring operations from being performed.

[0198] Meanwhile, the step S916 may further include a step of repeating the steps S910 to S914 a preset number of times or more. In this case, the arc monitoring control unit (200) may perform the steps S910 to S914 again if the sum of the frequency components related to the occurrence of the arc is greater than or equal to a preset reference size. In addition, if the sum of the frequency components having a value greater than or equal to a preset reference size is calculated a preset number of times during a certain period of time as a result of repeating the steps S610 to S614, it may be determined that an arc has occurred in the power line (50).

[0199] Meanwhile, separately from the arc monitoring performed by the arc monitoring control unit (200), the insulation monitoring control unit (300) can perform insulation monitoring. Therefore, the insulation monitoring can be performed while the arc monitoring is being performed. In this case, the insulation monitoring process of the insulation monitoring unit (30) may be the same as or similar to the operation process of the insulation monitoring unit (30) described in FIG. 6. Accordingly, the operation process of the insulation monitoring unit (30) will be omitted.

[0200] Meanwhile, the insulation monitoring system (1) according to an embodiment of the present invention monitors the insulation status of the power line (50) by determining whether an arc has occurred in the power line (50) based on the detection result of the arc monitoring unit (20) during a time when the insulation monitoring unit (30) cannot calculate the insulation resistance, and when the insulation resistance is calculated, the insulation status of the power line (50) can be monitored based on the insulation resistance.

[0201] FIG. 10 is a flowchart illustrating an operation process of a blocking unit (10) that performs insulation monitoring of a power line (50) by linking the arc monitoring unit (20) and the insulation monitoring unit (30) based on a voltage stabilization period according to polarity inversion of a pulse signal in the insulation monitoring unit (30) as an example of an insulation monitoring system (1) according to an embodiment of the present invention in such a case. As with FIG. 7, the blocking unit (10) of FIG. 10 also receives the sum of the magnitudes of at least one frequency component related to arc occurrence among frequency components decomposed according to a fast Fourier transform and the calculated insulation resistance, and thereby directly determines the insulation status of the power line (50).

[0202] Referring to FIG. 10, the control unit (100) of the blocking unit (10) can first detect whether the polarity of the pulse signal has been inverted in the insulation monitoring unit (30) (S1000). To this end, step S620 of FIG. 9 may further include a step in which, when the polarity of the pulse signal has been inverted, the insulation monitoring control unit (300) transmits the notification signal to the control unit (100). In this case, step S1000 may be a step in which a pulse signal polarity inversion signal has been received from the insulation monitoring unit (30).

[0203] If the detection result of the above step S1000 is that the polarity of the pulse signal has been inverted, the control unit (100) can check whether the insulation monitoring unit (30) has entered the voltage stabilization phase (S1002). To this end, the control unit (100) can check whether the insulation monitoring unit (30) has entered the voltage stabilization state based on whether insulation resistance has been received from the insulation monitoring unit (30) after a notification signal notifying the polarity inversion of the pulse signal has been received (S1002).

[0204] If, as a result of the check in step S1002, the insulation monitoring unit (30) has not entered the voltage stabilization state, the control unit (100) can receive the sum size of at least one frequency component related to arc occurrence among the frequency components decomposed according to the fast Fourier transform from the arc monitoring unit (20) (S1004). Then, it can be checked whether the sum size is greater than or equal to a preset reference size (S1006). Here, information on the reference size can be stored in the memory (120) of the blocking unit (10).

[0205] As a result of the determination in step S1006, if the sum size received from the arc monitoring unit (20) is greater than or equal to the reference size, the control unit (100) can output a blocking signal for the semiconductor circuit breaker (110) to block the load from the power line (50) even though the insulation resistance is not received from the insulation monitoring unit (30) (S1008). In addition, in order to prevent unnecessary operation of the insulation monitoring unit (30), an operation stop signal can be transmitted to the insulation monitoring unit (30) (S1010). Similarly, the control unit (100) can transmit an operation stop signal to the arc monitoring unit (20).

[0206] Meanwhile, if the result of the determination in step S1006 is that the sum size received from the arc monitoring unit (20) is less than the reference size, the control unit (100) can proceed to step S1002 again to check whether the insulation monitoring unit (30) has entered the voltage stabilization state. If the result of the check in step S1002 is that the insulation monitoring unit (30) has not entered the voltage stabilization state, the process from step S1004 to step S1006 can be performed again. That is, insulation monitoring according to the detection result of the arc monitoring unit (20) can be continuously performed until the insulation resistance is received from the insulation monitoring unit (30).

[0207] On the other hand, if the insulation monitoring unit (30) has entered the voltage stabilization state as a result of the check in step S1002, that is, if the insulation resistance is received from the insulation monitoring unit (30), the control unit (100) can compare the received insulation resistance with the reference value previously stored in the memory (120) (S1012). And if the insulation resistance is lower than the reference value as a result of the comparison in step S1012, the semiconductor circuit breaker (110) can output a blocking signal to block the load from the power line (50) (S1014). And, in order to prevent unnecessary operation of the arc monitoring unit (20), an operation stop signal can be transmitted to the arc monitoring unit (20) (S1016). Similarly, the control unit (100) can transmit an operation stop signal to the insulation monitoring unit (30).

[0208] However, if the insulation resistance is higher than the reference value as a result of the comparison at step S1012, it can be determined that the insulation condition of the power line (50) is good. Therefore, the blocking unit (10) can proceed to step S1000 again to check whether the pulse signal polarity reversal notification signal received from the insulation monitoring unit (30) has been received.

[0209] Then, when the insulation monitoring unit (30) reverses the polarity of the pulse signal to calculate the next insulation resistance, the pulse signal polarity reverse notification signal is received by the blocking unit (10) again, and the process proceeds from step S1000 to step S1002, so that the insulation status of the power line (50) can be monitored through arc monitoring until the insulation monitoring unit (30) enters the voltage stabilization state according to the polarity reverse of the pulse signal, and through insulation monitoring after the insulation monitoring unit (30) enters the voltage stabilization state.

[0210] Meanwhile, in the above description of the present invention, specific embodiments have been described, but various modifications can be implemented without departing from the scope of the present invention. In particular, in the embodiment of the present invention, an example of using a pattern of change in the intensity of a high-frequency current signal to determine whether an arc has occurred in an AC current and using a sum of frequency components corresponding to a preset frequency band among frequency components of the high-frequency current signal to determine whether an arc has occurred in a DC current has been described. However, it is of course possible to detect an arc in an AC current or an arc in a DC current in other ways.

[0211] Fig. 11a is a block diagram illustrating the configuration of an insulation monitoring device (1000) according to another embodiment of the present invention. Fig. 11b is a conceptual diagram illustrating an example in which an arc monitoring unit and an insulation monitoring unit of an insulation monitoring device (1000) according to another embodiment of the present invention are connected to a power line.

[0212] First, referring to FIG. 11a, an insulation monitoring device (1000) according to another embodiment of the present invention may be configured to include a control unit (1100), an arc monitoring unit (1120), an insulation monitoring unit (1130), and a blocking unit (1110) connected to the control unit (1100), and a memory (1150).

[0213] To be more specific, the above-mentioned blocking unit (1110) may be provided on a power line connecting a power source and a load or a power line connecting a system and a system.

[0214] Referring to Fig. 11b, when the left side of the blocking unit (1110), i.e., A, is connected to a power source, the right side of the blocking unit (1110), i.e., B, can be connected to a load. Conversely, in Fig. 11b, when the right side (B) of the blocking unit (1110) is connected to a power source, the left side (A) of the blocking unit (1110) can be connected to a load. In this way, when one side is a power source and the other side is a load, a one-way current flow can be formed. In addition, A and B may be different power systems, such as different micro grids, in which case a two-way current flow can be formed not only from the A system to the B system, but also from the B system to the A system.

[0215] In order to connect or block such one-way or two-way current flow, the blocking unit (1110) may include a semiconductor circuit breaker including at least one semiconductor switch. In addition, the blocking unit (1110) may be configured to be driven according to a control signal received from the control unit (1100) to block the electrical connection between the power source and the load whose insulation is damaged. In addition, the blocking unit (1110) may be configured to include not only the semiconductor circuit breaker that electrically blocks the connection between the load and the power source, but also a blocking switch that physically blocks the connection between the load and the power source.

[0216] And the arc monitoring unit (1120) can detect information related to the occurrence of an arc based on partial discharge that occurs when insulation breakdown occurs. The arc monitoring unit (1120) can detect information related to the occurrence of an arc in different ways when an AC current flows through the power line and when a DC current flows through the power line. For example, if the power line is a power line through which an AC current flows, the arc monitoring unit (1120) can detect a pattern of intensity change for a high-frequency current signal over a certain period of time based on the high-frequency current signal detected from the power line. On the other hand, if the power line is a power line through which a DC current flows, the arc monitoring unit (1120) can detect information on the magnitudes of preset frequency components related to the occurrence of an arc among the frequency components of the high-frequency current signal detected from the power line. And the detected information can be transmitted to the control unit (1100).

[0217] Then, the control unit (1100) can determine whether an arc has occurred in the power line based on arc-related information provided from the arc monitoring unit (1120), i.e., information on the signal intensity change pattern or information on the size of preset frequency components.

[0218] For example, if the provided arc-related information is information on a signal intensity change pattern, the control unit (1100) can compare the provided signal intensity change pattern with a preset signal intensity change pattern stored in the memory (1150), for example, a preset signal intensity change pattern (hereinafter, arc signal intensity change pattern) of a high-frequency current signal generated when an arc occurs in a power line through which an alternating current flows. As a result of the comparison, it is possible to determine whether an arc occurs in the power line based on whether the signal intensity change pattern provided from the arc monitoring unit (1120) matches the arc signal intensity change pattern, or based on whether the signal intensity change pattern provided from the arc monitoring unit (1120) matches the arc signal intensity change pattern a specified number of times or more during a preset time.

[0219] On the other hand, if the provided arc-related information is information on the size of preset frequency components, the control unit (1100) can compare the sum of the sizes of the preset frequency components with a preset reference size stored in the memory (1150), for example, a reference value obtained by summing the sizes of frequency components of a high-frequency current signal that occurs above a certain size when an arc occurs in a power line through which a direct current flows. Then, as a result of the comparison, whether an arc occurs in the power line can be determined based on whether the sum of the sizes of each frequency component provided from the arc monitoring unit (1120) matches the reference size stored in the memory (1150). Then, if it is determined that an arc has occurred, it is determined that the insulation of the power line has been damaged, and the blocking unit (1110) can be driven to cut off the electrical connection between the power source and the load.

[0220] Meanwhile, the arc monitoring unit (1120) may operate in different modes, for example, an AC arc detection mode and a DC arc detection mode, depending on whether an AC current flows in the power line or a DC current flows. Alternatively, the arc monitoring unit (1120) may have different configurations depending on whether it is placed in a power line where an AC current flows or a power line where a DC current flows. That is, an arc monitoring unit that detects an arc in a power line where an AC current flows may have a different configuration from an arc monitoring unit that detects an arc in a power line where a DC current flows.

[0221] For such arc detection, the arc monitoring unit (1120) may have various configurations, such as a high frequency current transformer (HFCT) for detecting a high frequency current signal from a power line. Hereinafter, the configuration of the arc monitoring unit (1120) will be examined in more detail with reference to FIG. 12a.

[0222] Meanwhile, the insulation monitoring unit (1130) can calculate insulation resistance in a power line through which a direct current flows or a power line through which an alternating current flows. In order to calculate the insulation resistance, the insulation monitoring unit (1130) applies a square wave pulse signal having a preset voltage to a virtual circuit formed between the power line and the ground, and calculates the insulation resistance (Re) based on the voltage distributed by the virtual resistance (insulation resistance (Re)) between the power line and the ground and the internal resistance (Ri) of the insulation monitoring unit (1130) from the applied pulse signal. Then, the calculated insulation resistance can be provided to the control unit (1100).

[0223] Then, the control unit (1100) can determine the insulation status of the power line based on the insulation resistance provided from the insulation monitoring unit (1130). For example, if the provided insulation resistance is lower than a preset reference value, the control unit (1100) can determine that the insulation of the power line has been destroyed (insulation damage). Then, the control unit (1100) can drive the cutoff unit (1110) to cut off the electrical connection between the power source and the load.

[0224] Meanwhile, the control unit (1100) can control each connected component and control the overall operation and function of the insulation monitoring device (1000). As described above, the control unit (1100) can determine the insulation status of the power line based on the arc-related information provided from the arc monitoring unit (1120) and the insulation resistance provided from the insulation monitoring unit (1130). Then, based on the determined insulation status of the power line, the control unit (1110) can be driven to cut off the electrical connection between the power source and the load.

[0225] In addition, the control unit (1100) can link the arc monitoring function of the arc monitoring unit (1120) and the insulation monitoring function of the insulation monitoring unit (1130) with each other. For example, the control unit (1100) can control the arc monitoring unit (1120) and the insulation monitoring unit (1130) so that the arc detection according to the monitoring function of the arc monitoring unit (1120) and the insulation resistance calculation according to the monitoring function of the insulation monitoring unit (1130) are performed continuously in time series, with the insulation monitoring state according to the insulation resistance calculation of the insulation monitoring unit (1130) as a trigger condition. The arc monitoring unit (1120) and insulation monitoring unit (1130) control operation process of the control unit (1100) will be described in detail with reference to a plurality of flowcharts illustrated in FIG. 14 and below.

[0226] Meanwhile, the memory (1150) stores data supporting various functions of the insulation monitoring device (1000). The memory (1150) can store data and commands for the operation of multiple application programs or applications running on the insulation monitoring device (1000) or each component constituting the insulation monitoring device (1000).

[0227] For example, the memory (1150) can store data for the arc monitoring function of the arc monitoring unit (1120). For example, as data for the arc monitoring function, the memory (1150) can store information on the sampling time point for sampling a high-frequency current signal and the number of signal intensities to be sampled for detecting an arc occurring in a power line through which an AC current flows, i.e., an AC arc, and information on an arc signal intensity change pattern that can determine whether an arc has occurred by comparing it with a signal intensity change pattern provided by the arc monitoring unit (1120). In addition, when a signal intensity change pattern matching the arc signal intensity change pattern is detected, information on a reference time and a reference number of times for comparing the number of times and the time at which the signal intensity change pattern matching the arc signal intensity change pattern is detected can be stored.

[0228] In addition, the memory (1150) may include information on at least one frequency band (arc frequency band) related to arc occurrence in order to detect an arc occurring in a power line through which a direct current flows, i.e., a direct current arc. The arc frequency band may be a frequency band including a specific frequency component that is included in a high-frequency current signal generated when the direct current arc occurs and has a certain size or more. In this case, the arc monitoring unit (1120) may decompose the high-frequency current signal into each frequency component, and detect frequency components included in at least one arc frequency band stored in the memory (1150) among the decomposed frequency components. In addition, the magnitude of the detected frequency components may be transmitted to the control unit (1100) as the arc-related information.

[0229] Here, the arc frequency band is a frequency band related to the occurrence of a direct current arc, and may be obtained through previously investigated statistical data or multiple arc occurrence experiments conducted in relation to the present invention. The arc frequency band may be stored in advance in the memory (1150), or may be downloaded or updated through wireless or wired communication.

[0230] In addition, the memory (1150) can store various data for the insulation monitoring function of the insulation monitoring unit (1130). For example, the memory (1150) can include information about the voltage of the pulse signal that the insulation monitoring unit (1130) applies to the power line and the time for which the pulse signal maintains a characteristic polarity, i.e., the time for which the polarity of the pulse signal is inverted. That is, when the polarity of the pulse signal is inverted, the insulation monitoring unit (1130) can maintain the polarity of the inverted pulse signal for the polarity inversion time stored in the memory (1150), and when the polarity inversion time expires, can invert the polarity of the pulse signal again.

[0231] Additionally, the memory (1150) can store data for voltage sampling to detect voltage stabilization according to the polarity inversion of the pulse signal in the insulation monitoring unit (1130). For example, information about the initial waiting time for the first sampling after the polarity of the pulse signal is inverted or the sampling interval can be stored in the memory (1150).

[0232] Meanwhile, the memory (1150) can store data input or output for the operation of the control unit (1100). For example, the memory (1150) can store arc-related data provided from the arc monitoring unit (1120) and insulation resistance provided from the insulation monitoring unit (1130). In addition, as reference data for comparing the arc-related data or insulation resistance, the insulation resistance reference value and the arc signal intensity change pattern or the arc frequency component magnitude reference value can be stored. In addition, for the control of the blocking unit (1110), data for driving the blocking unit (1110), for example, data for the threshold voltage of a semiconductor circuit breaker and data for controlling a blocking switch, etc. can be stored.

[0233] Hereinafter, referring to FIGS. 12a to 13, the configuration of each component of the insulation monitoring device (1000) according to an embodiment of the present invention will be examined in more detail.

[0234] FIG. 12a is a block diagram illustrating components provided in an arc monitoring unit (1120) according to an embodiment of the present invention.

[0235] Referring to FIG. 12a, the arc monitoring unit (1120) may be configured to include a high frequency current transformer (HFCT) (1121) for detecting a high frequency current signal, a filter unit (1122) for frequency filtering, a power detector (1123) for detecting the signal intensity of the high frequency current signal, and a voltage detector (1124) for detecting a voltage change of a power line. In addition, the arc monitoring unit (1120) may be configured to include a fast Fourier transformer (FFT) (1125) for decomposing the high frequency current signal into each frequency component.

[0236] First, the HFCT (1121) can detect a high-frequency current signal from a power line. The high-frequency current signal is a signal in a high-frequency band generated by partial discharge caused by an arc, and can also be referred to as a high-frequency noise signal.

[0237] And the filter unit (1122) may be a filter that filters a specific frequency in a frequency mask manner. Here, the specific frequency may be a frequency corresponding to living noise, noise generated when driving a load, or electromagnetic noise (EMC (ElectroMagnetic Compatibility) Noise). The filter unit (1122) is a filter that filters signals of at least one different frequency band that is designated in advance, and can remove noise whose frequency band is known in advance, such as living noise, driving noise of a load, or electromagnetic noise.

[0238] The signal intensity detection unit (1123) can detect the intensity of the high-frequency current signal detected through the HFCT (1121). For example, the signal intensity detection unit (1123) can convert the high-frequency current signal detected by the HFCT (1121) into a voltage signal corresponding to its intensity. Here, since the high-frequency current signal converted into the voltage signal may be an analog signal, the signal intensity detection unit (1123) may further include an analog-to-digital converter (ADC) for converting the high-frequency current signal in the analog form into a digital signal. Accordingly, the high-frequency current signal converted into the voltage signal can be converted into a digital signal having different values ​​depending on the signal intensity through the signal intensity detection unit (1123).

[0239] In addition, the signal intensity detection unit (1123) may further include an amplifier (not shown) that can amplify the intensity of the converted high-frequency current signal into a signal of a level that the control unit (1100) can identify. The amplifier may be an inverting amplifier that inverts the phase of an input signal and amplifies the inverted signal phase according to a voltage gain having a negative (-) value, or a non-inverting amplifier that maintains the phase of the input signal as it is and amplifies only the magnitude thereof according to a voltage gain having a positive (+) value.

[0240] Meanwhile, the voltage detection unit (1124) can detect a voltage change of the power line. In this case, if the current flowing in the power line is a single-phase current, the current flowing in the power line may be a current in which a positive (+) voltage and a negative (-) voltage periodically change according to the cycle of the single-phase current. Accordingly, a voltage change in which the positive (+) voltage and the negative (-) voltage periodically change is detected through the voltage detection unit, and the control unit (1100) can detect a ZCP (Zero Crossing Point) of the single-phase current based on the voltage change. Here, the ZCP is a point in time when the polarity is reversed according to the cycle characteristic of the alternating current, and may mean a point in time when the voltage becomes 0 according to the voltage change of the alternating current.

[0241] Meanwhile, the control unit (1100) can detect the point in time when the voltage changes from a positive (+) value to a negative (-) value, or the point in time when the voltage changes from a negative (-) value to a positive (+) value, i.e., the zero crossing points, based on the voltage change detected through the voltage detection unit (1124) when the power line is a power line through which an alternating current flows.

[0242] And the control unit (1100) can detect a high-frequency current signal through the HFCT (1121). And, based on the detection result of the signal intensity detection unit (1123), the change in the high-frequency current signal intensity over time can be detected. In this case, the control unit (1100) can detect the change in the high-frequency current signal intensity corresponding to a half cycle of the current flowing in the power line based on the zero crossing points. And, based on the pattern indicated by the change in the high-frequency current signal intensity during the detected half cycle, it can be determined whether an arc has occurred.

[0243] For example, a voltage difference occurs between adjacent points where insulation is damaged or destroyed, that is, between the two contact points of the circuit where the insulation is damaged or destroyed (hereinafter referred to as arc contact points), and a discharge phenomenon, that is, an arc, occurs according to the voltage difference that occurs. However, since the single-phase current has a characteristic in which the voltage periodically increases and decreases according to the periodic characteristic of the alternating current (e.g., zero crossing point), the voltage difference at the arc contact point also has a pattern of periodically increasing and decreasing. Accordingly, the high-frequency current signal generated by the arc may also have a pattern of increasing and decreasing according to the periodic pattern of the alternating current (e.g., ZCP).

[0244] For example, looking at the periodic characteristics when an AC arc occurs, the AC arc progresses from a state in which no arc occurs (No Arc state (No Arcing) - No Arc stage) as the voltage difference between the arc contacts is low, to a state in which an arc begins to occur at the arc contacts as the voltage difference between the arc contacts gradually increases (Arc Strikes state - Arc Strike stage), and in the Arc Strike state, progresses to a state in which the arc contacts are electrically connected through a discharge current as the voltage difference between the arc contacts reaches a maximum value (Arc Conducts state - Arc Conduct stage), and as the voltage difference between the arc contacts gradually decreases, progresses to a state in which the arc extinguishes in the Arc Conduct state (Arc Quenches state - Arc Quenches stage). And again, it can have a periodic characteristic of progressing from an arc quench state to a no arc state, progressing through the stages of no arc - arc strike - arc conduct - arc quench.

[0245] In this case, the intensity of the high-frequency current signal may be different in each of the no-arc stage, the arc strike stage, the arc conduct stage, and the arc quench stage. For example, the arc strike stage and the arc quench stage may be stages in which the voltage difference between the arc contacts is large and the arc is generated at its largest, since the current does not flow despite having a large voltage. In other words, these may be stages in which the high-frequency current signal is generated at its strongest.

[0246] In addition, the arc conduction stage is a stage where current is conducted between the arc contacts due to the arc discharge, and may be a stage where the arc decreases even though the voltage is at its highest. Therefore, it may be a stage where the intensity of the high-frequency noise current signal decreases. In addition, the no-arc stage is a stage where the arc does not occur or is extinguished due to a small voltage difference between the arc contacts, and may be a stage where the intensity of the high-frequency current signal is the weakest because the arc occurs the least.

[0247] Therefore, in the arc strike phase and the arc quench phase, a higher frequency current signal with a stronger intensity than in the arc conduct phase and the no-arc phase may be generated, and in the no-arc phase, a higher frequency current signal with a weaker intensity than the high frequency current signal generated in the arc conduct phase may be generated.

[0248] Accordingly, when examining the change in intensity of the high-frequency current signal due to the occurrence of an AC arc, when proceeding from the no-arc stage (ZCP), the arc strike stage, the arc conduct stage, and the arc quench stage to the no-arc stage (ZCP) again, the intensity of the high-frequency current signal increases as it proceeds from the no-arc stage to the arc strike stage, decreases as it proceeds again to the arc conduct stage, increases again as it proceeds from the arc conduct stage to the arc quench stage, and decreases again as it proceeds to the no-arc stage, having an increase-decrease-increase-decrease pattern, and may have a characteristic that the intensity of the high-frequency current signal in the arc conduct stage is weaker than that in the no-arc stage. Accordingly, the control unit (1100) may determine that an arc has occurred in the power line if the monitoring result of the arc monitoring unit (1120) for the power line through which the AC current flows (the intensity change pattern and characteristics of the high-frequency current signal) is detected at least once during a certain period of time.

[0249] Meanwhile, the above arc monitoring unit (1120) can detect an arc according to the intensity change pattern of the high-frequency current signal according to the section between ZCPs as described above in the case of a power line through which an alternating current flows, but it may be difficult to detect an arc using the above method in the case of a direct current flowing without a change in polarity. Accordingly, the arc monitoring unit (1120) can be configured to include an FFT (1125) that analyzes the frequency component of the high-frequency current signal detected by the HFCT (1121) in order to detect an arc in a power line through which a direct current flows, i.e. a direct current arc.

[0250] If the power line is a power line through which direct current flows, the FFT (1125) can perform a fast Fourier transform on a high-frequency current signal detected from the power line. Accordingly, the high-frequency current signal generated when a direct current arc occurs can be decomposed into each frequency component.

[0251] Then, the arc monitoring unit (1120) can detect at least one frequency component (arc frequency component) related to the occurrence of a DC arc among the decomposed frequency components based on at least one arc frequency band stored in the memory (1150). And, the magnitude of the detected arc frequency components can be transmitted to the control unit (1100). Alternatively, the control unit (1100) can obtain the magnitude of at least one frequency component based on the arc frequency band from each frequency component obtained by decomposing the high-frequency current signal as a result of the fast Fourier transform of the arc monitoring unit (1120). Then, the control unit (1100) can determine whether an arc (DC arc) has occurred in the power line based on the magnitude of the obtained frequency components.

[0252] Meanwhile, in the above description, it was explained as an example that the arc monitoring unit (1120) includes all components including the FFT (1125) so that it can detect both an AC arc that occurs when an AC current flows in a power line and a DC arc that occurs when a DC current flows, but it is of course possible to have only some components for detecting an AC arc or a DC arc.

[0253] For example, if the arc monitoring unit (1120) only monitors an AC arc (when an AC current flows in the power line), the arc monitoring unit (1120) may be configured with only an HFCT (1121), a filter unit (1122), a signal strength detection unit (1123), and a voltage detection unit (1124). On the other hand, if the arc monitoring unit (1120) only monitors a DC arc (when a DC current flows in the power line), the arc monitoring unit (1120) may be configured with only an HFCT (1121) and an FFT (1125). That is, depending on the current flowing in the power line, the arc monitoring unit (1120) may have different components and may determine whether an arc has occurred in different ways.

[0254] FIG. 12b is a block diagram illustrating components provided in an insulation monitoring unit (1130) according to an embodiment of the present invention.

[0255] An insulation monitoring unit (1130) of an insulation monitoring device (1000) according to an embodiment of the present invention may include a coupler resistor connected to power lines, a signal generating unit (1131) that applies a square wave pulse signal to the power lines through the coupler resistor, a signal measuring unit (1132) that includes a virtual insulation resistance formed between the power lines and a ground, and a detection resistor connected to the ground, a steady-state voltage detecting unit (1133) that receives a voltage measured by the signal measuring unit, calculates an average voltage according to a pulse signal applied to the power lines during a preset sampling period, and calculates a steady-state voltage after a voltage instability state due to polarity inversion of the pulse signal has passed based on an error with the average voltage calculated previously, and an insulation resistance calculating unit (1134) that calculates the size of the insulation resistance based on the calculated steady-state voltage and a steady-state voltage calculated for a pulse signal of a different polarity, which is calculated before the polarity inversion of the pulse signal.

[0256] First, the signal generation unit (1131) can generate a pulse signal having a constant positive (+) voltage or a constant negative (-) voltage for a preset period of time under the control of the control unit (1100). Then, the generated pulse signal can be applied to the power line. Accordingly, a pulse signal in which positive and negative voltages alternate based on the preset period of time can be applied to the power line under the control of the insulation monitoring control unit (300).

[0257] Meanwhile, the power line and ground may be connected to each other through a virtual circuit. A virtual insulation resistance may be formed between the power line and the ground. Furthermore, a virtual capacitor may be further formed between the power line and the ground. The virtual capacitor, together with the insulation resistance, may form an insulation impedance between the power line and the ground.

[0258] Accordingly, the pulse signal applied to the power line can be input to the signal measuring unit (1132) through the insulation resistor and capacitor through the virtual circuit formed between the power line and the ground. Then, the signal measuring unit (1132) can detect the voltage of the virtual circuit in which the insulation impedance is reflected based on the voltage at both ends of the detection resistor. Meanwhile, the detection result of the signal measuring unit (1132) can be amplified to an identifiable size and converted to a digital value. To this end, the signal measuring unit (1132) can be configured to include an amplifier (Amp, Amplifier, not shown) and an ADC (Analog Digital Converter) (not shown) that converts the voltage measured by the signal measuring unit (1132) into a digital value.

[0259] Meanwhile, the insulation resistance can be calculated based on the virtual circuit voltage for pulse signals of different polarities. However, if the voltage changes from positive to negative or vice versa, the polarity of the pulse signal changes from negative to positive, which can induce discharge and charge of the insulating capacitor. This causes a transient period in which the voltage increases by several times more than the applied pulse voltage, and the voltage of the virtual circuit becomes unstable. In such an unstable virtual circuit voltage, the insulation resistance cannot be accurately calculated.

[0260] Accordingly, the control unit (1100) can detect a change in the voltage of the virtual circuit measured by the signal measurement unit (1132) according to a preset sampling interval, and control the insulation monitoring unit (1130) to determine whether the virtual circuit voltage is stabilized based on the detected voltage change.

[0261] To this end, the control unit (1100) can control the signal measurement unit (1132) so that the voltage of the virtual circuit is detected at each preset sampling interval. In addition, the steady-state voltage detection unit (1133) can calculate the average voltage of the virtual circuit measured by the signal measurement unit (1132) during the sampling period according to the sampling interval according to the control of the control unit (1100). In addition, when the difference between the calculated average voltage and the average voltage calculated during the previous sampling period is less than or equal to a preset error value, it can be determined that the voltage of the virtual circuit is stabilized.

[0262] Meanwhile, when the steady-state voltage is calculated by the steady-state voltage detection unit (1133), the insulation resistance calculation unit (1134) can calculate the size of the insulation resistance based on the stabilized virtual circuit voltage (first steady-state voltage) calculated before the polarity of the pulse signal is inverted and the stabilized virtual circuit voltage (second steady-state voltage) calculated after the polarity of the pulse signal is inverted. Then, the calculated insulation resistance can be transmitted to the control unit (1100).

[0263] Then, the control unit (1100) can determine the insulation status of the power line based on the size of the received insulation resistance. That is, if the insulation resistance is below a preset reference value, the power line is determined to be in a state of insulation damage and the cutoff unit (1110) can be operated. Then, the electrical connection between the power source and the load can be cut off.

[0264] However, if the size of the received insulation resistance is greater than the reference value, the control unit (1100) can determine that the insulation condition of the power line is good. Then, the control unit (1100) can control the signal generation unit (1131) again to reverse the polarity of the pulse signal and control the insulation monitoring unit (1130) so that the insulation resistance is calculated.

[0265] Meanwhile, the insulation monitoring unit (1130) can determine the insulation status of a power line for not only direct current but also alternating current. For example, in the case of alternating current, the insulation monitoring unit may further include a converter (not shown) for converting the alternating current of the power line into direct current. In this case, a pulse signal can be applied to the power line through which the alternating current flows through the converter, and the alternating current detected from the power line can be converted into direct current through the converter. In addition, the signal measuring unit (1132) can detect the voltage of the converted direct current. Accordingly, the insulation monitoring unit (1130) can monitor the insulation status of not only the power line through which the direct current flows but also the power line through which the alternating current flows.

[0266] Fig. 13 is a block diagram showing a detailed configuration of a blocking unit of an insulation monitoring device according to an embodiment of the present invention.

[0267] As shown in Fig. 13, the circuit breaker (1110) may include a semiconductor circuit breaker composed of a plurality of semiconductor switches (112-1, 112-2) connected in series to connect a bidirectional current flow. Here, the semiconductor circuit breaker may be a solid state circuit breaker (SSCB) capable of high-speed current interruption.

[0268] In this way, by connecting a plurality of semiconductor switches in series, each of which has a source terminal and a drain terminal connected to different ends of the semiconductor circuit breaker, the circuit breaker (1110) can be formed to control the flow of bidirectional current flowing from side B to side A as well as the current flowing from side A to side B.

[0269] Meanwhile, the source terminal and the drain terminal of each of the first semiconductor switch (112-1) and the second semiconductor switch (112-2) may be connected through the gate terminal of each semiconductor switch. Each gate terminal is connected to each gate driver (111-1, 111-2), and the source terminal and the drain terminal may be electrically connected based on the voltage applied to the gate terminal from the gate driver, i.e., the gate voltage. In this case, if the gate voltage is higher than a preset threshold voltage, the source terminal and the drain terminal may be electrically connected. On the other hand, if the gate voltage is lower than the threshold voltage or the gate voltage is not applied, the source terminal and the drain terminal may not be electrically connected. That is, the electrical connection between the A side and the B side may be cut off.

[0270] Meanwhile, the control unit (1100) can control the gate driver (111-1, 111-2) of each semiconductor switch so that the electrical connection between the A side and the B side is cut off by adjusting the gate voltage applied to the gate terminal of each semiconductor switch (112-1, 112-2).

[0271] Here, the control unit (1100) can control the blocking unit (1110) based on the arc monitoring result (e.g., signal intensity change pattern or arc frequency components) received from the arc monitoring unit (1120) or the insulation status monitoring result (e.g., insulation resistance) received from the insulation monitoring unit (1130).

[0272] The description of Fig. 13 above illustrates an example in which two semiconductor switches (111-1, 111-2) are connected in series so that a bidirectional current flow can be formed. However, if the power line is a unidirectional circuit in which current flows in one direction, it goes without saying that only one semiconductor switch may be provided.

[0273] In the above description, the configuration of an insulation monitoring device (1000) according to an embodiment of the present invention has been described.

[0274] In the following description, the operation process of the insulation monitoring device (1000) according to the embodiment of the present invention described above will be examined in more detail with reference to a plurality of flowcharts.

[0275] First, FIG. 14 is a flowchart illustrating the operation process of an insulation monitoring device according to an embodiment of the present invention.

[0276] Referring to FIG. 14, the control unit (1100) of the insulation monitoring device (1000) according to an embodiment of the present invention can apply a signal having a positive or negative voltage of a preset magnitude to the power line when the operation of the insulation monitoring device (1000) starts (S1400). In addition, the control unit (1100) can check whether a preset polarity inversion time has elapsed (S1401). In this case, when the polarity inversion time has elapsed, the control unit (1100) can apply a voltage of the same magnitude but opposite polarity to the power line. That is, a pulse signal whose voltage polarity is inverted based on the polarity inversion time can be applied to the power line. In addition, when the voltage polarity of the pulse signal is inverted, the time elapsed from the time when the pulse signal is applied can be initialized.

[0277] If the check result of the above step S1401 shows that the preset polarity reversal time has not been reached, the control unit (1100) can control the arc monitoring unit (1120) to detect a high-frequency current signal from the power line (S1406). Then, based on the arc-related information provided from the arc monitoring unit (1120) based on the detected high-frequency current signal, it can be determined whether an arc has occurred in the power line (S1408).

[0278] The process of detecting whether an arc occurs in the above step S1408 may vary depending on whether the power line is an AC power line or a DC power line. Referring to FIGS. 15A and 15B below, the operation process of the control unit (1100) for detecting an AC arc that occurs when the power line is an AC power line will be described, and the operation process of the control unit (1100) for detecting a DC arc that occurs when the power line is a DC power line will be described in detail with reference to FIG. 16.

[0279] Meanwhile, if it is determined that an arc has occurred in the power line as a result of the determination in step S1408, the control unit (1100) can drive the blocking unit (1110) to block the load from the power line (S1422). In this case, the control unit (1100) can control each gate driver (111-1, 111-2) to apply a gate voltage lower than a preset threshold voltage. Alternatively, the control unit (1100) can control each gate driver (111-1, 111-2) so that the gate voltage is not applied. In addition, the blocking switch (130) can be driven so that the power line and the load are physically blocked.

[0280] On the other hand, in step S1408, if it is determined that an arc has occurred based on the arc-related information received from the arc monitoring unit (1120), and the result is that no arc has occurred, the control unit (1100) can check whether the initial sampling time point for starting sampling has been reached to detect the point in time when the voltage stabilizes after a pulse signal of a specific polarity is applied. To this end, the control unit (1100) can check whether the time elapsed from the point in time when the voltage polarity of the pulse signal is reversed is longer than a preset initial waiting time (hereinafter, whether the initial waiting time has elapsed) and whether the insulation resistance corresponding to the voltage polarity of the pulse signal currently applied to the power line has been calculated (S1404).

[0281] Here, the initial waiting time is for starting sampling to detect the point in time when the voltage stabilizes after the polarity of the pulse signal is switched as described above, and may be the time from when the pulse signal of the specific polarity is applied until the initial sampling point in time is reached. Therefore, the initial waiting time is the time between when the polarity of the pulse signal is reversed and when the polarity is reversed again, and may be a time shorter than the polarity reversal time. Therefore, the polarity reversal time of the pulse signal may expire after the initial waiting time has elapsed from the point in time when the pulse signal of the specific polarity is applied.

[0282] In the above step S1404, the control unit (1100) can check whether the initial waiting time has elapsed since the time point at which a pulse signal of a specific polarity is applied, and whether the insulation resistance corresponding to the voltage polarity of the pulse signal currently applied to the power line has been calculated. In addition, if any of the conditions is not met, the control unit (1100) can proceed to step S1401 again to check whether the polarity reversal time of the polarity of the pulse signal has elapsed.

[0283] And if the check result of step S1401 shows that the polarity reversal time has not elapsed, the control unit (1100) can proceed to steps S1406 and S1408 again. Therefore, if the check result of step S1404 shows that the initial waiting time has not been reached from the time when the pulse signal of a specific polarity is applied, or even after the initial waiting time has elapsed, but the insulation resistance corresponding to the voltage polarity of the pulse signal currently applied to the power line has been calculated, the control unit (1100) can repeatedly perform the process of determining whether an arc has occurred based on a high-frequency current signal detected from the power line.

[0284] Meanwhile, if the result of the check in step S1404 indicates that the initial waiting time has been reached and the insulation resistance corresponding to the voltage polarity of the pulse signal currently applied to the power line has not been calculated, the control unit (1100) controls the insulation monitoring unit (1130) to detect the virtual circuit voltage between the power line and the ground detected by the signal measuring unit (320) as the initial value at the time when the initial waiting time has elapsed (S1410).

[0285] And the control unit (1100) can acquire the next sample according to the preset sampling interval (S1412). Here, the acquired sample may be the virtual circuit voltage calculated after the sampling interval has elapsed. And, the average voltage between the acquired samples can be calculated (S1414). In this case, the average voltage between the initial value and the next sample (the first sample) can be calculated.

[0286] Meanwhile, when the average voltage is calculated, the control unit (1100) can determine whether the voltage difference between the average voltage calculated in the previous sampling interval and the average voltage calculated in the current sampling interval is within a preset error range (S1416). If there is no average voltage calculated in the previous sampling interval, the voltage difference between the average voltages may fall outside the error range. Therefore, the control unit (1100) can proceed to step S1412 again to acquire the next sample (second sample) according to the sampling interval.

[0287] Then, in step S1414, the average voltage between the first sample and the second sample can be calculated. Then, the control unit (1100) can compare the currently calculated average voltage with the average voltage calculated in the previous sampling interval (average voltage between the initial value and the first sample) to determine whether the voltage difference is within the error range. If it is out of the error range, the process can proceed to step S1412 again, and the process from step S1412 to step S1414 can be repeated.

[0288] Meanwhile, if the voltage difference between the average voltages calculated in each sampling section is within the above error range as a result of the determination in step S1416, the control unit (1100) determines that the voltage instability phenomenon caused by the polarity inversion of the pulse signal has been resolved, and can determine the currently detected voltage as a voltage in a stable state, i.e., a normal voltage. Then, the control unit (1100) can calculate the insulation resistance based on the normal voltage determined before the polarity of the pulse signal was inverted and the currently determined normal voltage, i.e., the normal voltages determined when the polarities of the pulse signal are different (S1418).

[0289] And the control unit (1100) can compare the size of the calculated insulation resistance with a preset reference value (S1420). If the determined result of step S1420 shows that the calculated insulation resistance is lower than the preset reference value, the control unit (1100) can determine that the power line is in a state of insulation damage. Then, the control unit (1100) can control the cutoff unit (1110) to cut off the connection with the power line (S1422). In this case, step S1422 may include a step of driving the cutoff switch (150) to physically cut off the load from the power line.

[0290] On the other hand, if the insulation resistance calculated as a result of the determination in step S1420 is higher than the preset reference value, the control unit (1100) can determine that the insulation condition of the power line is good. Then, the control unit (1100) can proceed to step S1401 again. Accordingly, it can be checked whether the polarity inversion time for inverting the polarity of the pulse signal has expired. If the polarity inversion time has not yet expired, the control unit (1100) can proceed to step S1406 again to control the arc monitoring unit (1120) to detect a high-frequency current signal from the power line, and determine whether an arc has occurred through step S1408.

[0291] And if the determination result of step S1408 is that an arc has occurred, the control unit (1100) can proceed to step S1422 to drive the blocking unit (1110). However, if the determination result of step S1408 is that an arc has not occurred, the control unit (1100) can proceed to step S1404 again to check whether the initial waiting time has elapsed and the insulation resistance has not been calculated. In this case, since the insulation resistance corresponding to the voltage polarity of the pulse signal currently applied to the power line has been calculated, both conditions of step S1404 may not be satisfied. Accordingly, the control unit (1100) can proceed to step S1401 again to check whether the polarity inversion time of the pulse signal has expired.

[0292] And if the check result of the above step S1401 is that the polarity inversion time has expired, the control unit (1100) can invert the polarity of the signal applied to the power line (S1402). Accordingly, a signal with an inverted polarity can be applied to the power line, and a pulse signal whose polarity is inverted at a cycle of the polarity inversion time can be applied to the power line.

[0293] Meanwhile, if the polarity of the pulse signal is inverted in step S1402, the control unit (1100) may proceed to step S1404 to check whether an initial waiting time has elapsed since a pulse signal of a specific polarity was applied and whether an insulation resistance corresponding to the voltage polarity of the pulse signal currently applied to the power line, i.e., an insulation resistance corresponding to a pulse signal whose polarity is inverted, has been calculated. If both conditions of step S1404 are not met, the control unit may proceed to steps S1406 and S1408 again to determine whether an arc has occurred based on a high-frequency current signal detected from the power line before the preset initial waiting time is reached.

[0294] Meanwhile, FIG. 15a and FIG. 15b describe in more detail the operation process of detecting whether an arc has occurred in a power line through the arc monitoring unit (1120) in step S1408 when an AC current flows in the power line during the operation process of the insulation monitoring device described in FIG. 14.

[0295] First, referring to FIG. 15a, the control unit (1100) can control the arc monitoring unit (1120) to obtain samples from a high-frequency current signal detected from a power line (S1500).

[0296] For example, the control unit (1100) can determine sampling points at which to sample a preset number of samples at a time corresponding to a half cycle of the alternating current flowing in the ZCP, i.e., the power line.

[0297] As described above, when the insulation of a power line is broken, the voltage difference between the two contact points of the circuit (hereinafter referred to as arc contact points) increases or decreases over time due to the characteristics of alternating current, in which the voltage increases or decreases over time, and accordingly, the intensity of the arc also has a pattern of increasing or decreasing.

[0298] Referring to Fig. 15b, the periodic characteristics of arc generation and extinguishment are examined. As the voltage approaches 0 before and after the ZCP of the AC current, the voltage difference between the arc contacts decreases. Accordingly, the No Arc stage (1511, 1521) in which no arc is generated can be entered. However, as the voltage gradually increases past the ZCP, the voltage difference between the arc contacts increases, and accordingly, the Arc Strike stage (1512, 1522) in which the arc increases can be entered. In addition, when the voltage difference between the arc contacts reaches 1 / 4 cycle at which the voltage difference is at its maximum, some current is conducted between the arc contacts through the current discharged from the arc contacts, so the arc can be entered into the Arc Conduct stage (1513, 1523) in which the arc actually decreases. And as the voltage drops after the maximum value, the arc discharge also decreases, so the electrical connection between the arc contacts is broken again, and the arc can enter the Arc Quenches stage (1514, 1524) where the arc increases again. And after the Arc Quenches stage (1514, 1524) stage, the no-arc stage (1511, 1521) can enter again.

[0299] That is, in the case of an AC arc, the intensity of the arc has a relatively changing pattern depending on the periodic characteristics of the AC current flowing in the power line. Accordingly, the intensity of the high-frequency current signal may also have a pattern in which the signal intensity changes similarly to the no-arc phase - arc strike phase - arc conduct phase - arc quench phase - no-arc phase between ZCP and ZCP of the AC current, that is, during a half cycle of the AC current.

[0300] In order to detect such a signal intensity change pattern, the control unit (1100) can obtain a preset number of samples at points in time corresponding to each phase of the AC arc. In this case, the control unit (1100) can determine a point in time corresponding to ZCP, which is the point in time when the voltage is the lowest, and a point in time corresponding to 1 / 4 cycle, which is the point in time when the voltage is the highest, as the first and third points in time for performing sampling corresponding to the no-arc phase and the arc conduct phase, respectively. In addition, the points in time between the first and third points in time and between the points in time corresponding to the next ZCP after the third point in time can be determined as the second and fourth points in time for performing sampling corresponding to the arc strike phase and the arc quench phase, respectively.

[0301] For example, the second point in time may correspond to 1 / 8 cycle of the AC current, and the fourth point in time may correspond to 3 / 8 cycle of the AC current. In this case, the first to fourth points in time may correspond to ZCP, 1 / 8 cycle, 2 / 8 (1 / 4) cycle, and 8 / 3 cycle, respectively. It should be understood that the sampling points described above are merely examples to assist in explaining the present invention, and the present invention is not limited thereto.

[0302] Hereinafter, a preset number of high-frequency current signals sampled based on the first time point will be referred to as first samples, and a preset number of high-frequency current signals sampled based on the second time point will be referred to as second samples. Similarly, the high-frequency current signals sampled at the third and fourth time points will be referred to as third samples and fourth samples, respectively. Here, the first samples may be samples obtained in the no-arc step (1511, 1521), and the second samples may be samples obtained in the arc strike step (1512, 1522). In addition, the third samples may be samples (1513, 1523) obtained in the arc conduct step, and the fourth samples may be samples obtained in the arc quench step (1514, 1524).

[0303] When sampling for each sampling point is completed in the step S1500, the control unit (1100) can calculate the signal intensity average of the high-frequency current signals sampled for each point (S1502). Accordingly, the signal intensity average (first signal intensity average) for the first samples acquired in the no-arc step (1511, 1521) can be calculated. In addition, the signal intensity average (second signal intensity average) for the second samples acquired in the arc strike step (1512, 1522) can be calculated. In addition, the signal intensity averages (third signal intensity average and fourth signal intensity average) for the third and fourth samples acquired in the arc conduct step (1513, 1523) and the arc quench step (1514, 1524) can be calculated.

[0304] Then, the control unit (1100) can detect the intensity change pattern of the high-frequency current signal from the signal intensity averages of each arc stage (S1504). For example, the control unit (1100) can detect the change in the signal intensity average when the cycle of the AC current progresses from the ZCP point to the 1 / 8 cycle point by comparing the first signal intensity average and the second signal intensity average. In addition, the control unit (1100) can detect the change in the signal intensity average when the cycle of the AC current progresses from the 1 / 8 cycle point to the 2 / 8 cycle point (1 / 4 cycle) by comparing the second signal intensity average and the third signal intensity average. In the same manner, the control unit (1100) can compare the third signal average and the fourth signal average, and can compare the fourth signal average with the first signal average of the next cycle, to detect the change in the signal intensity average when the cycle of the AC current progresses from the 2 / 8 cycle point to the 3 / 8 cycle point, and from the 3 / 8 cycle point to the 4 / 8 cycle point (half cycle, i.e., ZCP).

[0305] And the control unit (1100) can determine whether the detected average signal intensity change pattern matches a signal intensity change pattern previously stored in the memory (1150), for example, a preset signal intensity change pattern of a high-frequency current signal generated when an AC arc occurs (hereinafter, arc signal intensity change pattern) (S1506).

[0306] For example, if an arc occurs, the intensity of the high-frequency current signal may be the weakest in the no-arc phase (around the ZCP) (1511), and then increase as the arc strike phase (1512) is entered. Then, as the current is conducted after the arc strike phase (1512) and enters the arc conduct phase (maximum voltage state, 1 / 4 cycle) (1513), the intensity of the high-frequency current signal may decrease again. Then, as the current conduction is interrupted as the arc conduct phase (1513) enters the arc quench phase (1514), the intensity of the high-frequency current signal may increase again, and as the no-arc phase (1521), which is the ZCP state, the intensity of the high-frequency current signal may weaken again.

[0307] Therefore, if an arc occurs, the change in the signal intensity average may increase when moving from the first signal average to the second signal average, decrease when moving from the second signal average to the third signal average, increase again when moving from the third signal average to the fourth signal average, and decrease again when moving from the fourth signal average to the first signal average of the next cycle. That is, the change pattern of the signal intensity average may have a pattern of increase - decrease - increase - decrease, and may have a characteristic in which the intensity of the third signal intensity average is greater than that of the first signal intensity average.

[0308] Accordingly, the control unit (1100) can determine that a pattern corresponding to arc occurrence has been formed when a change pattern of the average signal intensity and a feature (a feature in which the intensity of the third signal intensity average is greater than that of the first signal intensity average) are detected in step S1506. Accordingly, if the detected change pattern of the average signal intensity matches the arc signal intensity change pattern, the control unit (1100) can proceed to step S1420 of FIG. 14 to drive the blocking unit (1110) so that the load is blocked from the power line.

[0309] However, if the change pattern of the detected average signal intensity matches the arc signal intensity change pattern, the control unit (1100) may proceed to step S1404 of FIG. 14 to determine whether an initial waiting time has elapsed since the time point at which a pulse signal of a specific polarity is applied and whether an insulation resistance corresponding to the polarity of the voltage signal currently applied to the power line has been calculated, and may proceed to step S1401 of FIG. 14 again or step S1410 of FIG. 14 to detect an initial value depending on the determination result of step S1404 of FIG. 14. In this case, if proceeding to step S1401 of FIG. 14, the operation process of FIG. 15a may be performed again depending on whether a polarity signal inversion signal has elapsed.

[0310] Meanwhile, the control unit (1100) may, of course, determine whether an arc has occurred based on whether a pattern of change in the average signal intensity corresponding to the arc occurrence pattern has been detected a preset number of times over a certain period of time in order to more accurately determine whether an arc has occurred. In this case, the step S1506 may be a step of determining whether a pattern of change in the average signal intensity corresponding to the arc signal intensity change pattern has been detected a preset number of times over a certain period of time.

[0311] Meanwhile, Fig. 16 is a more detailed description of the operation process of detecting whether an arc has occurred in a power line through the arc monitoring unit (1120) in step S1408 when a direct current flows in the power line during the operation process of the insulation monitoring device described in Fig. 14.

[0312] Referring to FIG. 16, the control unit (1100) can decompose the high-frequency current signal obtained in step S1406 of FIG. 14 into each frequency component (S1600). To this end, the control unit (1100) can control the FFT (1125) to perform a fast Fourier transform on the obtained high-frequency current signal.

[0313] And the control unit (1100) can detect frequency components corresponding to at least one preset frequency band (arc frequency band) among the frequency components of the decomposed high-frequency current signal (S1602). Here, the at least one preset frequency band may be a frequency band of a high-frequency current signal that is generated above a certain size when an arc occurs in a power line through which a direct current flows. That is, the at least one arc frequency band is a frequency band related to arc generation, and may be obtained through statistical data investigated in advance or a plurality of arc generation experiments conducted in relation to the present invention.

[0314] When frequency components included in at least one arc frequency band are detected among the frequency components of the high-frequency current signal decomposed in the above step S1602, the control unit (1100) can add up the magnitudes (signal magnitudes) of each of the detected frequency components (S1604). Then, the added signal magnitude can be compared with a preset reference magnitude (S1606).

[0315] If the signal size added in the above step S1606 is greater than or equal to the preset reference size, the control unit (1100) may determine that an arc has occurred. Then, the control unit (1100) may proceed to step S1420 of FIG. 14 to drive the blocking unit (1110) so that the load is blocked from the power line.

[0316] However, if the signal size added in step S1606 is less than the preset reference size, the control unit (1100) may determine that an arc has not occurred. Then, the control unit (1100) may proceed to step S1404 of FIG. 14 to determine whether an initial waiting time has elapsed since the time when a pulse signal of a specific polarity is applied in step S1606 and an insulation resistance corresponding to the polarity of the voltage signal currently applied to the power line has been calculated, and may proceed to step S1401 again or step S1410 of FIG. 14 to detect an initial value depending on the determination result of step S1404 of FIG. 14. In this case, if step S1401 of FIG. 14 is proceeded, the operation process of FIG. 16 may be performed again depending on whether a polarity signal inversion signal has elapsed.

[0317] Meanwhile, since only one of AC current and DC current normally flows in the power line, either the operation process of FIG. 15a or the operation process of FIG. 16 may be selectively performed depending on the current flowing in the power line. In this case, the control unit (1100) may preset the operation mode of the arc monitoring unit (1120) depending on the current flowing in the power line, or the configuration of the arc monitoring unit (1120) may be preset with components for detecting either an AC arc or a DC arc depending on the current flowing in the power line.

[0318] Fig. 17 is a conceptual diagram illustrating arc monitoring and insulation monitoring performed by an insulation monitoring device (1000) according to an embodiment of the present invention. Hereinafter, Fig. 17 will be examined with reference to the flowchart of Fig. 14.

[0319] When a pulse signal is applied in step S1400 of FIG. 14, the control unit (1100) can detect whether an arc has occurred based on a high-frequency current signal detected from the power line until a preset initial waiting time has elapsed in a state where the insulation resistance is not calculated in step S1404 of FIG. 14. In this case, the initial waiting time is calculated from the point in time when the voltage polarity of the pulse signal is inverted, and can be shorter than the polarity inversion time when the voltage polarity of the pulse signal is inverted. Therefore, the expiration of the initial waiting time can be reached before the voltage polarity of the pulse signal is inverted again.

[0320] In addition, since the insulation resistance is not calculated when the initial waiting time is not reached, as shown in FIG. 17, the insulation monitoring device (1000) according to an embodiment of the present invention can continuously monitor the insulation status of the power line through whether or not the arc occurs during the time from the time point (1710, 1720) at which polarity reversal occurs until the initial waiting time elapses.

[0321] Meanwhile, when the initial waiting time (tn) has elapsed (1711), the control unit (1100) starts sampling based on the judgment result of step S1404 of FIG. 14 (whether the initial waiting time has elapsed and insulation resistance has not been calculated) and can detect the voltage measured from the virtual circuit between the power line and the ground as the initial value (t01). Then, sampling is continued from after the initial value to calculate the average voltage of each sampling section, and when the difference between the calculated average voltages is less than or equal to a preset error value, the calculated average voltage can be determined as the steady-state voltage.

[0322] And when the above steady-state voltage is determined, the control unit (1100) can calculate the insulation resistance based on the steady-state voltage determined before the polarity of the pulse signal is reversed, i.e., when the polarity of the pulse signal is a different polarity, and the currently determined steady-state voltage (tr2) (1701). And when the insulation resistance is calculated, the insulation status of the power line can be determined based on the calculated insulation resistance. Therefore, after the initial waiting time (tn) has elapsed, the insulation status of the power line can be monitored based on the calculated insulation resistance.

[0323] However, when the voltage polarity of the pulse signal is reversed, a voltage instability phenomenon as shown in Fig. 17 occurs due to charging and discharging of the insulation capacitance of the virtual circuit between the ground and the power line. In the case of this voltage instability phenomenon, it may vary depending on the size of the insulation capacitance, but since the insulation capacitance of the virtual circuit is not known, it is difficult to accurately specify the point in time when the insulation resistance is calculated after the voltage polarity of the pulse signal is reversed. Accordingly, there is a problem in that it is difficult for the conventional insulation monitoring device to monitor the insulation status of the power line until the polarity of the pulse signal is reversed again after the insulation resistance is calculated and the insulation status is determined.

[0324] However, in the case of the insulation monitoring device (1000) according to an embodiment of the present invention, if the insulation resistance calculated as a result of the determination in step S1420 is equal to or higher than the reference value as shown in FIG. 14, the process proceeds to step S1401 again to check whether the voltage polarity inversion time of the pulse signal has elapsed, and if the polarity inversion time has not elapsed, the process proceeds to step S1406 again to determine whether an arc has occurred according to the high-frequency current signal.

[0325] Meanwhile, since the determination of whether an arc occurs in the high-frequency current signal is repeated until both conditions of step S1404 of FIG. 14, which determines whether a preset initial waiting time has elapsed while the insulation resistance is not calculated, are met, as shown in FIG. 17, from the time point (tr1) (1712) when the insulation resistance is calculated, to the time point (tr2) (1721) when the initial waiting time (tn), which is calculated again from the time point when the voltage polarity of the pulse signal is inverted (tk2) (1720), has elapsed, that is, until the time point when sampling for calculating the insulation resistance again begins, the determination of whether an arc occurs in the high-frequency current signal can be made.

[0326] That is, the insulation monitoring device (1000) according to an embodiment of the present invention performs insulation monitoring using the insulation resistance during a time when insulation resistance is calculated and insulation monitoring is possible based on the insulation resistance after the initial standby time has elapsed, and performs insulation monitoring based on whether an arc occurs based on a high-frequency current signal detected from a power line during the remaining time. Accordingly, there is an effect of minimizing the blank period during which insulation monitoring of the power line is not performed.

[0327] Meanwhile, in the description of the present invention described above, specific embodiments have been described, but various modifications can be implemented without departing from the scope of the present invention. In particular, in the embodiment of the present invention, when an AC current flows in a power line, a configuration has been described in which the occurrence of an arc (AC arc) is determined based on a pattern according to a change in the average signal intensity of samples acquired with respect to ZCP as a reference, and when a DC current flows, the occurrence of an arc (DC arc) is determined based on a frequency component of a high-frequency current signal included in a pre-stored arc frequency band. However, it is to be understood that the present invention is not limited thereto. In other words, it is to be understood that the AC arc or DC arc can be determined using any number of other methods.

[0328] The present invention described above can be implemented as computer-readable code on a medium in which a program is recorded. The computer-readable medium includes all types of recording devices that store data that can be read by a computer system. Examples of computer-readable media include hard disk drives (HDDs), solid state disks (SSDs), silicon disk drives (SDDs), ROMs, RAMs, CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, etc., and also includes media implemented in the form of carrier waves (e.g., transmission via the Internet). In addition, the computer may include a control unit (100) of a blocking unit (10). Therefore, the above detailed description should not be construed as limiting in all respects, but should be considered as illustrative. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are intended to be included in the scope of the present invention.

Claims

1. An arc monitoring unit that detects a high-frequency current signal from a power line connecting a power source and a load and monitors the occurrence of an arc due to insulation damage of the power line based on the detected high-frequency current signal; An insulation monitoring unit that calculates insulation resistance between the power line and ground and monitors the insulation status of the power line based on the calculated insulation resistance; A circuit breaker for breaking the electrical connection between the power line and the load depending on whether a blocking signal is received; and An insulation monitoring system characterized by comprising a control unit connected to the arc monitoring unit and the insulation monitoring unit, receiving at least one of an insulation monitoring result related to the occurrence of the arc from the arc monitoring unit and an insulation monitoring result related to the insulation resistance from the insulation monitoring unit, and outputting the blocking signal to the circuit breaker based on the received insulation monitoring result.

2. In paragraph 1, The insulation monitoring results received from the above arc monitoring unit are: Contains a signal intensity change pattern of a high-frequency current signal detected from the above power line, The above control unit, An insulation monitoring system characterized in that the insulation status of the power line is determined based on whether the signal intensity change pattern matches a previously stored arc pattern.

3. In the second paragraph, the control unit, An insulation monitoring system characterized in that, when the signal intensity change pattern matches the stored arc pattern, it is determined whether the signal intensity change pattern detected from the high-frequency current signal for a certain period of time matches the stored arc pattern a preset number of times, and the insulation status of the power line is determined based on the determination result.

4. In paragraph 1, The insulation monitoring results received from the above arc monitoring unit are: It includes the magnitude of frequency components included in at least one preset frequency band among the frequency components of a high-frequency current signal detected from the above power line, The above control unit, An insulation monitoring system characterized by monitoring the insulation status of a power line based on the magnitude of frequency components included in the insulation monitoring results.

5. In paragraph 4, the arc monitoring unit, A High Frequency Current Transformer (HFCT) that detects the high frequency current signal from the power line; FFT (Fast Fourier Transformer) that decomposes the high-frequency current signal into the size of each frequency component; A memory including information about at least one frequency band related to a high-frequency current signal generated when an arc occurs; and An insulation monitoring system characterized by comprising an arc monitoring control unit that detects at least one frequency component among each frequency component of the decomposed high-frequency current signal, which is included in at least one frequency band stored in the memory, and transmits the insulation monitoring result including the magnitude of the detected frequency components to the control unit.

6. In paragraph 1, the insulation monitoring unit, An insulation monitoring system characterized in that when the polarity of a pulse signal applied to the power line is reversed, a notification signal notifying the polarity inversion is transmitted to the control unit, and when the insulation resistance corresponding to the pulse signal whose polarity is reversed is calculated, the calculated insulation resistance is transmitted to the control unit.

7. In paragraph 6, the control unit, When the above notification signal is received from the above insulation monitoring unit, the insulation status of the power line is monitored based on the insulation monitoring result received from the arc monitoring unit until the insulation resistance calculated by the above insulation monitoring unit is received. An insulation monitoring system characterized in that the insulation status of the power line is monitored based on the insulation monitoring result received from the insulation monitoring unit when the insulation resistance is received.

8. In paragraph 1, The above circuit breaker is, At least one semiconductor switch including a source terminal connected to the power side of the power line, a drain terminal connected to the load side of the power line, and a gate terminal electrically connecting the source terminal and the drain terminal based on an applied gate voltage, and a gate driver applying the gate voltage to the gate terminal, The above control unit, An insulation monitoring system characterized in that the gate driver is controlled to apply a gate voltage lower than a preset threshold voltage based on an insulation monitoring result received from at least one of the arc monitoring unit and the insulation monitoring unit.

9. A control method for an insulation monitoring system including an arc monitoring unit that monitors the occurrence of an arc due to insulation damage of a power line, an insulation monitoring unit that calculates insulation resistance between the power line and ground, and a blocking unit that blocks a load from the power line. A step of transmitting a notification signal to the blocking unit notifying the polarity inversion of the pulse signal when the insulation monitoring unit reverses the polarity of the pulse signal applied to the power line for calculating insulation resistance; The above-mentioned blocking unit, when the notification signal is received, receives a first insulation monitoring result related to the occurrence of the arc from the arc monitoring unit; The step of the above-mentioned blocking unit determining the insulation status of the power line based on the first insulation monitoring result; A step for the above-mentioned blocking unit to block the load from the power line when insulation damage is detected as a result of the insulation status determination according to the first insulation monitoring result; A step in which the insulation monitoring unit calculates insulation resistance and transmits the calculated insulation resistance to the blocking unit while the blocking unit determines the insulation status of the power line based on the first insulation monitoring result; The step of the above-mentioned blocking unit, when the insulation status determination result according to the first insulation monitoring result does not detect insulation damage, receiving the insulation resistance and judging the insulation status of the power line based on the received insulation resistance; and, A control method for an insulation monitoring system, characterized in that the above-mentioned blocking unit includes a step of blocking a load from the power line according to the result of the trial.

10. In paragraph 9, The step of determining the insulation status of the power line based on the first insulation monitoring result is as follows: The step of the above blocking unit receiving the size of at least one preset frequency component from the arc monitoring unit; and, The above-mentioned blocking unit determines the insulation status of the power line based on the magnitude of the received frequency components, The magnitude of the frequency components received from the above arc monitoring unit is A control method for an insulation monitoring system, characterized in that the arc monitoring unit extracts frequency components based on at least one frequency band related to arc occurrence among frequency components of a high-frequency current signal detected from the power line.

11. An arc monitoring unit that detects high-frequency current signals from power lines connecting power sources and loads and collects analysis results from analyzing the detected high-frequency current signals; An insulation monitoring unit for calculating insulation resistance between the power line and ground; A circuit breaker for blocking the connection between the power source and the load; and An insulation monitoring device characterized in that it comprises a control unit which determines the insulation status of the power line using either the analysis result of the high-frequency current signal or the insulation resistance depending on whether or not the insulation resistance is calculated, and controls the disconnection unit to disconnect the connection between the power source and the load according to the determination result, the polarity inversion time from when the voltage polarity of the pulse signal applied by the insulation monitoring unit to the power line is inverted until the voltage polarity is inverted again, the initial waiting time from when the voltage polarity of the pulse signal is inverted until initial sampling is performed, and the like.

12. In paragraph 11, The analysis results of the above high-frequency current signal are as follows: Contains a signal intensity change pattern of a high-frequency current signal detected from the above power line, The above control unit, An insulation monitoring device characterized in that the insulation status of the power line is determined based on whether the signal intensity change pattern matches a previously stored arc signal intensity change pattern.

13. In paragraph 12, The above signal intensity change pattern is, It is a pattern according to the change in intensity of a high-frequency current signal detected at each of a first point in time when the AC current flowing in the power line reaches ZCP (Zero Crossing Point), a second point in time between a third point in time corresponding to 1 / 4 cycle of the AC current, and a fourth point in time between the third point in time and the point in time when the ZCP is reached again. The above arc signal intensity change pattern is, An insulation monitoring device characterized by a pattern corresponding to a step-wise signal intensity change of a high-frequency current signal that occurs when an arc occurs in the above power line.

14. In the 13th paragraph, the arc monitoring unit, An insulation monitoring device characterized in that, based on each of the first to fourth time points, a preset number of intensity samples of the high-frequency current signal are acquired, the acquired samples are averaged for each time point to calculate an average signal intensity for each time point, and a pattern of change in the average signal intensity for each time point is detected as the signal intensity change pattern.

15. In paragraph 11, The analysis results of the above high-frequency current signal are as follows: It includes the magnitude of frequency components detected based on at least one preset frequency band among frequency components of a high-frequency current signal detected from the above power line, The above control unit, An insulation monitoring device characterized by monitoring the insulation status of the power line based on the magnitude of the detected frequency components.

16. In paragraph 11, the control unit, When the above initial waiting time has elapsed, the insulation monitoring unit is controlled to calculate the insulation resistance, and the insulation status of the power line is determined based on the calculated insulation resistance. An insulation monitoring device characterized in that, when the insulation resistance is calculated, the insulation status of the power line is determined based on the analysis result of analyzing the high-frequency current signal received from the arc monitoring unit until the initial waiting time has elapsed again for the pulse signal whose voltage polarity has been reversed after the voltage polarity of the pulse signal has been reversed again.

17. In the control method of the insulation monitoring device of Article 11, A step of checking whether a first condition, which is satisfied depending on whether the time elapsed from the time a pulse signal having a certain size of positive or negative voltage is applied to a power line has elapsed a preset initial waiting time, and a second condition, which is satisfied depending on whether the insulation resistance has been calculated, are both satisfied; A step of determining whether an arc has occurred in the power line based on a high-frequency current signal detected from the power line until both the first and second conditions are met, if neither of the first and second conditions is met; A step of calculating the insulation resistance between the power line and the ground when both the first and second conditions are satisfied in a state where the arc has not occurred as a result of determining whether the arc has occurred; A step of determining the insulation status of the power line based on the size of the calculated insulation resistance when the above insulation resistance is calculated; and, A control method for an insulation monitoring device, characterized in that it comprises a step of repeatedly performing a step of checking whether both the first and second conditions are satisfied based on the result of determining the insulation status, and a step of determining the insulation status of the power line based on the size of the insulation resistance.

18. In paragraph 17, The step of checking whether both the first and second conditions above are met is: A step of checking whether the polarity inversion time of the preset pulse signal has elapsed; and, If the above polarity inversion time has elapsed, the step of inverting the voltage polarity of the pulse signal is further included. A control method for an insulation monitoring device, characterized in that when the polarity reversal time has elapsed, the required time is reset.

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