Arc monitoring device and control method thereof

Abstract

The present invention comprises: a high-frequency signal detection unit for detecting high-frequency signals from an electric line; an interruption unit for interrupting the electrical connection between a power source and a load by interrupting an electric line; a voltage detection unit for detecting voltage changes in an electric line; a current detection unit for detecting current changes in an electric line; and a control unit for detecting, from the voltage changes, ZCPs which are time points at which the voltage reaches a reference voltage according to phase alternation thereof, estimating whether an arc occurs during a half-cycle of the current corresponding to the interval between the detected ZCPs on the basis of the average intensity of high-frequency signals and the current magnitude detected during the half-cycle, determining whether an arc has occurred in an electric line on the basis of whether the estimated number of times of arc occurrence is equal to or greater than a reference number, and interrupting the electric line according to the determination result.

Description

Arc monitoring device and control method thereof

[0001] The present invention relates to an arc monitoring device for monitoring an arc and a control method of the device.

[0002] Arcing typically refers to an electrical spark or spark. It refers to a discharge phenomenon that occurs when a high potential difference occurs between positive and negative terminals, characterized by high current density. These arcs can be caused by damage to wires or electrical appliances, insulation breakdown, connection defects, or aging. They can also cause fires if there are flammable materials nearby, making them a major cause of electrical fires.

[0003] Meanwhile, conventional leakage circuit breakers or overcurrent circuit breakers are basically designed to prevent leakage or short circuits, and their circuit breaker function can be activated when a current exceeding a preset size is detected for a certain period of time. However, arcs can occur even at low currents of 3 to 5 A or less, and it is difficult to detect arcs occurring at such low currents or arcs occurring for less than a certain period of time with leakage circuit breakers or overcurrent circuit breakers. Accordingly, various countries are mandating the installation of arc circuit breakers that can block such arcs, and research into detecting and blocking arcs is actively underway.

[0004] As part of this research, an arc detection device has been developed that detects noise in a current signal and uses the magnitude of the high-frequency component of the detected noise to detect the occurrence of an arc. However, current arc detection devices only determine whether an arc has occurred based on the magnitude of a specific high-frequency component detected from the current noise, which limits their ability to distinguish between typical current noise and arcs. Consequently, there is a problem that the accuracy of arc detection is not high, such as misidentifying noise as arcs or misjudging arcs as noise.

[0005] In order to increase the accuracy of such arc detection, methods have emerged that set a specific frequency band of interest for the noise generated when an arc occurs, and determine whether or not an arc occurs by determining whether noise occurs in the set frequency band of interest. However, this method has the problem that it is difficult to detect arc noise that occurs in an area outside the frequency band of interest. In addition, due to the technological development of current power conversion devices, arc noise has the characteristic of occurring in the form of white noise that occurs across a wide frequency band rather than a specific band of frequencies, and as described above, there is the problem that it is difficult to accurately detect an arc by monitoring in a specific frequency band of interest.

[0006] The present invention aims to solve the above-mentioned problems and other problems, and its purpose is to detect the occurrence of an arc by using high-frequency noise occurring over a wide frequency band.

[0007] In order to achieve the above or other purposes, according to one aspect of the present invention, an arc monitoring device according to an embodiment of the present invention is characterized by including a high-frequency signal detection unit for detecting a high-frequency signal from a current flowing in an electric circuit, a blocking unit for blocking the electric circuit to block an electrical connection between a power source and a load, a voltage detection unit for detecting a voltage change in the electric circuit, a current detection unit for detecting a current change in the electric circuit, and a control unit for detecting a zero crossing point, which is a point in time having a reference voltage according to a phase alternation of voltage from the voltage change, and estimating whether an arc (ARC) occurs during the half cycle based on an average of the current magnitude detected during a half cycle of the current corresponding to a zero crossing point and the intensity of the high-frequency signal, and determining whether an arc occurs in the electric circuit based on whether the estimated number of arc occurrences is equal to or greater than a preset reference number, and controlling the blocking unit to block the electric circuit based on the determination result.

[0008] In one embodiment, the control unit determines the reference number of times based on the current size detected during the half cycle, and the reference number of times is determined to be smaller as the detected current size increases.

[0009] In one embodiment, the control unit is characterized in that it performs a current offset operation on current signals sampled during the half cycle and calculates an effective value for current signals in which a current greater than a certain size is detected, thereby calculating the current size.

[0010] In one embodiment, the control unit is characterized in that it determines whether an arc has occurred in the circuit based on whether the estimated number of times the arc has occurred during the time period in which the half cycle is repeated a preset number of times is greater than or equal to the reference number.

[0011] In one embodiment, the control unit is characterized in that, if the estimated number of arc occurrences during the time period in which the half cycle is repeated a preset number of times is less than the reference number, the estimated number of arc occurrences counted up to now is deducted from the estimated number of arc occurrences counted before the time period in which the half cycle is repeated a preset number of times.

[0012] In one embodiment, the arc monitoring device further comprises a ZCT (Zero-phase Current Transformer) for detecting leakage current, and the control unit further determines whether leakage current occurs in the circuit based on a detection result of the ZCT, and further controls the cutoff unit based on the determination result.

[0013] In one embodiment, the control unit is characterized in that it receives the zero crossing point detected according to the voltage change of the voltage detection unit as an interrupt signal, and starts sampling the current signal and the high-frequency signal when the interrupt signal is received.

[0014] In one embodiment, the high frequency signal detection unit is formed by including a high frequency current transformer (HFCT) and a high pass filter (HPF) formed to allow only high frequency signals above a preset frequency band to pass, and the current detection unit is formed by including at least one of a shunt resistor and a low frequency current transformer (LFCT).

[0015] In order to achieve the above or other purposes, according to one aspect of the present invention, a control method of an arc monitoring device according to an embodiment of the present invention comprises: a first step of detecting a zero crossing point, which is a point in time having a reference voltage according to a voltage change of a current flowing in a circuit; a second step of sampling a current signal and a high-frequency signal during a half cycle of the current corresponding to the detected zero crossing point and the zero crossing point when the zero crossing point is detected; a third step of increasing an arc check time count for checking an elapsed time; a fourth step of calculating an average value of the current signal magnitude and the high-frequency signal during the half cycle; a fifth step of estimating whether an arc has occurred during the half cycle in which the current signal and the high-frequency signal have been sampled based on the calculated magnitude of the current signal and the average value of the high-frequency signal; a sixth step of increasing an estimated number of arc occurrences when an arc occurrence is estimated, and checking whether the number of arc occurrences accumulated up to now is greater than or equal to a reference count; and a seventh step of cutting off the circuit to cut off the electrical connection between a power source and a load when the accumulated number of arc occurrences is greater than or equal to the reference count. and an 8th step of checking whether the accumulated arc check time count has reached a preset reference time count when the occurrence of an arc is not estimated in the 5th step or the accumulated number of arc occurrences is less than a reference count in the 6th step; a 9th step of re-performing the first step and the steps after the 1st step when the accumulated arc check time count has not reached the reference time count; and a 10th step of initializing the accumulated arc check time count and re-performing the first step and the steps after the 1st step when the accumulated arc check time count has reached the reference time count.

[0016] In one embodiment, the 10th step further includes a 10-1 step of deducting the number of times counted before a preset time from the accumulated number of arc occurrences, wherein the preset time is characterized in that the time corresponding to the case where the half cycle is repeated as many times as the number of reference time counts.

[0017] In one embodiment, the preset time is determined according to the frequency of the current flowing in the circuit, and when the reference time count and the frequency of the current flowing in the circuit are the same, the preset time is characterized in that it is 0.5 seconds.

[0018] In one embodiment, the fourth step is characterized by including a step 4-1 of performing a current offset operation on current signals sampled during the half cycle, and a step 4-2 of calculating an effective value for current signals in which a current greater than a certain size is detected as a result of the current offset operation to calculate the size of the current signal.

[0019] In one embodiment, the fourth step further includes a fourth-third step of determining the reference count based on the current magnitude detected during the half cycle, wherein the reference count is determined to be smaller as the detected current magnitude increases.

[0020] In one embodiment, the fifth step includes a 5-1 step of comparing the magnitude of the calculated current signal with a preset reference current, a 5-2 step of calculating an average value of the high-frequency signal when the magnitude of the calculated current signal exceeds the preset reference current, a 5-3 step of proceeding to the eighth step of checking whether the accumulated arc check time count has reached a preset reference time count when the magnitude of the calculated current signal is less than the preset reference current, a 5-4 step of estimating whether an arc occurred during the half cycle in which the current signal and the high-frequency signal were sampled when the average value of the calculated high-frequency signal exceeds the preset reference value, and a 5-5 step of proceeding to the eighth step of checking whether the accumulated arc check time count has reached a preset reference time count when the average value of the calculated high-frequency signal is less than the preset reference value.

[0021] In one embodiment, the high frequency signal is characterized as a high frequency noise signal detected through a high frequency current transformer (HFCT) and a high pass filter (HPF) formed to allow only high frequency signals above a preset frequency band to pass.

[0022] The effects of the arc monitoring device and the arc monitoring device control method according to the present invention are described as follows.

[0023] According to at least one of the embodiments of the present invention, the present invention detects high-frequency noise that occurs overall in a band of tens of MHz to hundreds of MHz, and estimates whether an arc has occurred based on a peak current during a half cycle and an average value of the detected high-frequency noise. Then, if the estimated number of arc occurrences reaches a preset number during a preset period of time, it is determined that an arc has occurred, and a trip control signal can be output so that a circuit breaker is operated. Accordingly, there is an effect that damage to a load and internal power devices due to the occurrence of an arc can be prevented.

[0024] In addition, the present invention has the effect of allowing the preset number of times for determining whether an arc has occurred to be adjusted according to the size of the peak current occurring during the half cycle, thereby allowing the occurrence of an arc to be determined more quickly in the case of a circuit through which a large current flows, and allowing the occurrence of an arc to be determined more accurately in the case of a circuit through which a small current flows.

[0025] Figure 1 is a conceptual diagram to explain the types of arcs according to their cause of occurrence.

[0026] Figure 2 is an example diagram showing an example of arc noise appearing in a wide frequency band in the form of white noise.

[0027] FIG. 3 is a block diagram illustrating the configuration of an arc monitoring device according to an embodiment of the present invention.

[0028] Figure 4 is a diagram showing typical high-frequency arc noise and current changes when an arc occurs.

[0029] FIG. 5 is a flowchart illustrating an operation process for determining whether an arc has occurred in an arc monitoring device according to an embodiment of the present invention.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] Figure 1 is a conceptual diagram to explain the types of arcs according to their cause of occurrence.

[0035] Referring to Fig. 1, Fig. 1 shows an example of an arc occurring in a single-phase circuit consisting of a live wire and a neutral wire. As described above, an arc is caused by insulation breakdown due to aging, deterioration, or physical damage, and can refer to a phenomenon in which an electrical discharge occurs between the two ends of a disconnected wire due to a gas acting as a conducting medium when at least a portion of the wire is disconnected. In other words, a state in which at least a portion of the wire is disconnected but current can flow due to an electrical discharge can be referred to as an 'arc'.

[0036] Even if only part of the circuit is disconnected, or even the entire circuit is disconnected, if current can be conducted through a gas, the electrical energy of the power source can be supplied to the load through the remaining portion or the gas that serves as the conducting medium. However, if current flows through the gas as the conducting medium, there is a risk of electrical fire because air discharge of electrical energy occurs in the surrounding area.

[0037] Meanwhile, such arcs may occur for individual reasons in each circuit. For example, in the case of a single-phase circuit consisting of a live line (L line) and a neutral line (N line) as shown in Fig. 1, arcs may occur in only one of the live lines and the neutral line as shown in Fig. 1 (a), or arcs may occur in all circuits, i.e., both the live line and the neutral line as shown in Fig. 1 (b).

[0038] For example, in cases such as aging or deterioration of a circuit, an arc may occur only in either the live wire or the neutral wire, as shown in (a) of Fig. 1. An arc occurring only in one circuit is referred to as a series arc hereinafter.

[0039] On the other hand, unlike the serial arc described above, as shown in (b) of Fig. 1, arcs can occur in both the live and neutral lines. For example, if strong physical pressure, such as from heavy equipment, is applied to both circuits, physical damage may occur to both circuits, and this physical damage may cause arcs to occur in both circuits. Hereinafter, an arc resulting from physical damage to both circuits will be referred to as a parallel arc.

[0040] Meanwhile, when such an arc occurs, electricity can be supplied to the load due to the discharge phenomenon that occurs between both ends of each disconnected circuit. Accordingly, when an arc occurs, the size of the arc changes around the ZCP (Zero Cross Point), which is a point with a reference voltage (e.g., 0 V) ​​as the polarity of the current switches. More specifically, the arc size increases as it moves away from the ZCP, and the arc size decreases as it moves closer to the ZCP, showing a cyclical characteristic.

[0041] Meanwhile, a noise signal including a typical noise, for example, switching noise (211), has the characteristic that its size decreases as the frequency increases, as shown in the noise signal (210) in FIG. 2. However, noise generated when an arc occurs has the characteristic of occurring in the form of white noise that occurs evenly throughout a wide frequency band ranging from tens of MHz to hundreds of MHz, as shown in the arc noise signal (200) in FIG. 2.

[0042] FIG. 3 is a block diagram illustrating the configuration of an arc monitoring device according to an embodiment of the present invention for monitoring parallel arcs in the form of white noise that occur in a wide frequency band ranging from tens of MHz to hundreds of MHz and have periodic characteristics in which the arc changes around the ZCP (Zero Cross Point) as such. FIG. 4 is an exemplary diagram for explaining the periodic characteristics of a high-frequency noise signal that occurs when an arc occurs and the current change when an arc occurs.

[0043] First, referring to FIG. 3, the arc monitoring device according to an embodiment of the present invention may be configured to include a blocking unit (350), a current detection unit (310), a voltage detection unit (320), a high frequency current transformer (HFCT) (330), a filter unit (331), an amplifier unit (332), a control unit (300), a communication unit (360), a memory (370), and an output unit (380). In addition, the device may further include a zero-phase current transformer (ZCT) (340). The components illustrated in FIG. 3 are not essential for implementing the arc monitoring device, and thus, the arc monitoring device described in this specification may have more or fewer components than the components listed above. In addition, each component of the arc monitoring device illustrated in FIG. 3 may be connected to the control unit (300) and may be controlled by the control unit (300).

[0044] First, the blocking unit (350) can block the electrical connection between the power source and the load when it is determined that an arc has occurred or a leakage current is generated. The blocking unit (350) can include a trip coil and a driving circuit for driving the trip coil, and the driving circuit can be driven according to a trip control signal provided from the control unit (300). That is, the blocking unit (350) can be driven according to the trip control signal provided from the control unit (300) to perform a blocking operation for blocking the connection between the load and the power source.

[0045] The current detection unit (310) can detect the amount of current flowing in the electric circuit connecting the power source and the load. The current detection unit (310) may include a preset shunt resistor or a low frequency current transformer (LFCT) to detect the amount of current. In this case, the current detection unit (310) can detect the amount of current based on the voltage difference measured at both ends of the shunt resistor or the low frequency current signal detected by the LFCT. In addition, the current detection unit (310) may be equipped with an LPF (Low Pass Filter) to remove noise from the measurement result, and may further include an amplifier to amplify the measured value to a level that the control unit (300) can recognize.

[0046] Here, a bimetallic component used in an arc monitoring device according to an embodiment of the present invention may be used as the shunt resistor. In this case, the current detection unit (310) may detect the amount of current flowing in the circuit based on the specific resistance value of the bimetallic component. In this case, a separate shunt resistor may not be provided.

[0047] And the voltage detection unit (320) can detect the voltage change of the electric circuit. In this case, if the current flowing in the electric circuit is a single-phase current, the current flowing between the power line and the internal line may be an alternating current whose voltage phase periodically alternates according to the cycle of the single-phase current. Accordingly, in the electric circuit, positive (+) voltage and negative (-) voltage may periodically alternate around the ZCP. Therefore, the control unit (300) can detect the ZCP based on the voltage change of the electric circuit.

[0048] Meanwhile, the HFCT (High Frequency Current Transformer) (330) is a sensor for detecting a high-frequency noise signal of a current flowing in a circuit, and may be formed so that any one of the circuits passes through it. In addition, the HFCT (330) may include at least one sensor for detecting a wide high-frequency noise signal ranging from several tens of MHz to several hundred MHz that is generated when a partial discharge or an arc occurs. Preferably, the HFCT (330) can detect a high-frequency noise signal ranging from 10 MHz to 150 MHz or from 10 MHz to 200 MHz.

[0049] In addition, the filter unit (331) is a HPF (High Pass Filter) formed to pass only high-frequency signals, and may be a filter that passes only signals in a high-frequency band ranging from tens of MHz to hundreds of MHz. In addition, the filter unit (331) may further include 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). That is, the filter unit (331) may be a filter that passes signals in a high-frequency band, and may be a filter that filters signals in at least one specific frequency band that is designated in advance so as not to pass. Through this, not only signals in a low-frequency band, but also noise whose frequency band is known in advance, such as living noise, driving noise of a load, electromagnetic noise, etc., can be removed.

[0050] And the amplifier (332) can receive the filtered high-frequency noise signal and amplify the received signal into a signal of a level identifiable by the control unit (300). The amplifier (332) can include an analog-to-digital converter (ADC) for converting an analog-type high-frequency current signal into a digital signal. In addition, the amplifier (332) can be a logarithmic amplifier whose input / output voltage ratio exhibits a logarithmic characteristic, which can indicate a wide input voltage range.

[0051] And the control unit (300) controls each component of the arc monitoring device and can control the overall operation of the arc monitoring device.

[0052] The control unit (300) can receive a high-frequency noise signal amplified through the amplifier unit (332). Then, it can detect a change in the intensity of the high-frequency noise signal over a certain period of time (e.g., half a cycle of a single-phase current), and determine whether an arc has occurred based on the change in the intensity of the high-frequency noise signal.

[0053] First, the control unit (300) can detect the zero crossing point based on the voltage change of the circuit detected by the voltage detection unit (320). Then, the interval between zero crossing points can be detected as a half cycle of the single-phase current flowing in the circuit. Then, based on the current amount detected during the half cycle, the peak current amount and the average value of the high-frequency noise signal can be calculated.

[0054] Fig. 4 (a) is an example diagram showing the characteristics of high-frequency arc noise, and Fig. 4 (b) is a diagram showing current changes according to the periodic pattern of the arc.

[0055] Referring to (a) of Fig. 4, when the current characteristic of the alternating current crosses from a positive voltage to a negative voltage, i.e., when the zero crossing point is approached, the voltage difference between adjacent arc contacts may decrease. And when the ZCP is reached, an arc may not occur. In this way, in the stage where an arc does not occur between the arc contacts, i.e., the no-arc stage (411), a high-frequency noise signal may hardly be detected because an arc does not occur.

[0056] However, depending on the characteristics of the alternating current, the supplied voltage may gradually increase as it passes the zero crossing point. Then, the voltage difference between the arc contacts may gradually increase. And when the voltage difference between the arc contacts exceeds a certain level, a discharge due to the accumulated voltage difference, i.e., an arc, may occur. Therefore, as it passes the no-arc stage (411) corresponding to the zero crossing point, the intensity and size of the high-frequency noise signal may increase as the arc is generated due to the increase in the voltage difference. In this way, as the voltage difference between the arc contacts increases, a stage in which the intensity of the high-frequency noise signal increases, i.e., the arc strike stage (412), may proceed.

[0057] Meanwhile, if the voltage difference between the arc contacts further increases and reaches a voltage level that allows current to flow through the gas, current may flow between the arc contacts on both sides of the shorted circuit due to the discharge phenomenon. In this case, as current flows through, the intensity of the high-frequency noise signal may decrease. In this way, when the voltage difference between the contacts reaches a certain level, the arc conduction stage (413) may proceed, in which current flows through the gas and the high-frequency noise signal is actually reduced.

[0058] In the arc conduction phase (413), if the voltage decreases again depending on the characteristics of the alternating current, a voltage sufficient to establish current flow may not be formed between the arc contacts on both sides. Then, current flow may be interrupted, causing the current flowing between the arc contacts to discharge into the air. Consequently, the arc quenching phase (414), in which the intensity of the high-frequency noise signal increases again, may begin.

[0059] Meanwhile, in the arc quenching stage (414), the voltage may be further reduced depending on the characteristics of the alternating current. The reduced voltage may then approach the zero crossing point again, and in this case, the voltage difference between the contacts may again approach zero. Then, the no-arc stage (421), in which no arc occurs, may proceed again.

[0060] When examining the change in the magnitude of the current at each stage of the arc, in the no-arc stage and the arc strike stage, the voltage between the contacts is insufficient for current to pass through the gas. Therefore, in the no-arc stage (411, 421), the arc strike stage (412, 422), and the arc quench stage (414, 424), the current flowing between the contacts of the circuit may be limited. However, since current passes through the arc conduct stage (413, 423), the current flow may rapidly increase in the arc conduct stage (413, 423). In this way, when the two arc contacts are electrically connected due to the voltage difference and the current flows between the two arc contacts, a current having a maximum value may flow. In this way, in the arc conduct stage (413, 423), the maximum current flowing due to current passing through the electrical discharge will be referred to as a peak current hereinafter.

[0061] Meanwhile, the control unit (300) may start sampling current and high-frequency noise signals based on the detection result of the voltage detection unit (320). When the zero-crossing point is detected, sampling of current and high-frequency noise signals may begin until the next zero-crossing point is detected. The current signals and high-frequency noise signals sampled in this manner may be the current amount and high-frequency noise signals during the half cycle. Then, the control unit (300) may calculate the peak current amount among the current amounts detected during the half cycle and calculate the average value of the high-frequency noise signals detected during the half cycle. Then, based on the calculated peak current amount and the average value of the high-frequency noise signal, it may be possible to estimate whether an arc occurred during the half cycle.

[0062] In this case, the control unit (300) can detect current amounts having a size greater than or equal to a preset size among the sampled current amounts as current samples corresponding to the peak current. Then, the control unit can perform a root mean square (RMS) operation on the detected current samples to calculate the peak current amount. Then, it can check whether the calculated peak current amount exceeds a preset reference current amount.

[0063] Additionally, the control unit (300) can check whether the average value of the generated high-frequency noise signal exceeds a preset reference value.

[0064] And, if the average value of the high-frequency noise signal exceeds the reference value while the peak current exceeds the reference current, it can be estimated that an arc occurred during the half cycle corresponding to the sampled signals.

[0065] And the control unit (300) can check whether the estimated number of arc occurrences has reached the preset number during the preset time. And if the estimated number of arc occurrences has reached the preset number, it can be determined that an arc has occurred during the half cycle. And a trip control signal for driving the blocking unit (350) so that the load is cut off from the power source can be output to the blocking unit (350).

[0066] Here, the control unit (300) can vary the preset reference number of times for determining whether an arc has occurred based on the estimated number of times the arc has occurred, depending on the magnitude of the current flowing through the circuit. In this case, the amount of current flowing through the circuit may be the peak current amount.

[0067] In this case, the greater the peak current, the greater the impact on the arc. For example, the greater the peak current, the greater the amount of electricity discharged by the arc. Accordingly, the risk of fire may increase. Accordingly, the control unit (300) sets the preset reference frequency to a lower value as the peak current increases, thereby cutting off the electrical connection between the load and the power source even when the estimated number of arc occurrences is low.

[0068] On the other hand, if the peak current is small, the impact on the arc may be small. For example, the smaller the peak current, the less electricity may be discharged by the arc. Accordingly, the risk of fire, etc. may be lower. However, if the power between the load and the power source is cut off, the load cannot receive electrical energy, which may cause unexpected damage to the user. Accordingly, the lower the peak current, the more accurately the occurrence of an arc can be determined, and the preset number of times can be set large so that the electrical connection between the load and the power source is cut off only when the occurrence of an arc is confirmed.

[0069] Meanwhile, the memory (370) can store a program for the operation of the control unit (300) and can store data input or output for performing the function of the arc monitoring device. For example, the memory (370) can store information on ZCP detected according to the voltage change detected by the voltage detection unit (320), and can store information on the current signal sampled by the current detection unit (310) and the high-frequency noise signal sampled by the HFCT (330). In addition, information on the current offset value for calculating the peak current and information on the average value (signal intensity average value) of the high-frequency noise signal calculated from samples between ZCPs, i.e., during a half cycle, can be stored.

[0070] In addition, the communication unit (360) can perform a wired or wireless communication connection with a preset external server or a preset terminal. The communication unit (360) can provide measured information to the external server or the preset external terminal through the wired or wireless communication connection. Here, the external server may be a management server that manages the arc monitoring device according to an embodiment of the present invention, and the external terminal may be a preset user's terminal. In this case, the user's terminal may be a mobile terminal, a smart phone, a tablet PC, a laptop, or a other portable terminal. Alternatively, the external terminal may be a wearable device that the user can wear, such as a smart watch or smart glasses. Alternatively, the external terminal may be a fixed terminal, such as a PC.

[0071] Meanwhile, the arc monitoring device may further include an output unit (380) for indicating the operating status of the arc monitoring device. The output unit (380) may include at least one of a light output unit and an audio signal output unit. The light output unit may include at least one LED capable of emitting light of different colors. In addition, the audio output unit may include at least one speaker or buzzer capable of outputting an audio signal. In the case of the light output unit, the operating status of the arc monitoring device may be indicated using light emitted from an LED or the like. In addition, in the case of the audio output unit, the operating status of the arc monitoring device may be indicated using an audio signal output from a speaker or the like.

[0072] In addition, the arc monitoring device may further include a Zero-phase Current Transformer (ZCT) (340) for detecting leakage current of the circuit. The ZCT can compare the magnitude of the current flowing from the power source to the load through the live line (L line) with the magnitude of the current flowing from the load to the power source through the neutral line (N line), and determine whether there is leakage current based on the difference. The ZCT (340) may be equipped with a Low Pass Filter (LPF) for filtering current noise. In this case, the arc monitoring device can detect whether a leakage current occurs based on the detection result of the ZCT (340). In addition, when a leakage current occurs, the circuit breaker (350) can be controlled to output a trip control signal and perform a circuit breaker operation.

[0073] Here, the above leakage current may be caused by an insulation breakdown at the ground. In this case, since the insulation breakdown means the occurrence of an arc, the above leakage current may correspond to an arc occurring at the ground, i.e., the occurrence of a ground arc. Therefore, the detection of the leakage current is to detect the occurrence of the ground arc, and accordingly, the arc monitoring device may determine whether a ground arc has occurred and, based on the determination result, may cut off the electrical connection between the power source and the load.

[0074] Meanwhile, the above ZCT (340) is an example of a leakage current detection unit for detecting leakage current, and it is obvious that the present invention is not limited thereto. That is, the arc monitoring device according to an embodiment of the present invention may use any other leakage current detection unit capable of detecting leakage current instead of the above ZCT (340).

[0075] FIG. 5 is a flowchart illustrating an operation process for determining whether an arc has occurred in an arc monitoring device according to an embodiment of the present invention.

[0076] The control unit (300) of the arc monitoring device according to an embodiment of the present invention can detect the point in time when the polarity of the voltage changes, i.e., the point in time when the voltage reaches 0 V, as ZCP based on the detection result of the voltage detection unit (320). Then, when ZCP is detected, current sampling and sampling of high-frequency noise signals can be started until the next ZCP is detected.

[0077] In this case, since ZCP occurs periodically every half cycle of the alternating current, the current signal and high-frequency noise signal sampled from ZCP until the next ZCP is reached may be the current signal and high-frequency noise signal sampled during the half cycle of the alternating current. That is, based on ZCP, the current signal and high-frequency noise signal can be sampled at a preset sampling interval every half cycle of the alternating current signal.

[0078] To this end, the control unit (300) can receive the ZCP detected according to the voltage change of the voltage detection unit (320) as an interrupt signal. When the interrupt signal is received, sampling of the current signal and the high-frequency noise signal can begin. The sampling can continue until the next interrupt signal is received, i.e., until the next ZCP is received, and sampling can be restarted when the next interrupt signal is received.

[0079] Therefore, each time a half-cycle of a current signal elapses, current signals and high-frequency noise signals sampled during each half-cycle can be collected. Fig. 5 may be an operation process that is performed when current signal samples and high-frequency noise signal samples are collected during a half-cycle in this manner.

[0080] Referring to FIG. 5, the control unit (300) of the arc monitoring device according to an embodiment of the present invention can first perform an offset operation on the current when current signal samples and high-frequency noise signal samples for a half cycle are collected. Here, the current offset operation may be a preprocessing process for detecting a peak current and an operation process for generating a reference current value. For example, the current offset operation may be a process for calculating a current below a certain size as a reference current value, for example, 0 A (Ampere).

[0081] When the above current offset operation is completed, the control unit (300) can increase the preset arc check time count by the preset count value (S500). Here, the arc check time count is used to check whether the reference time has elapsed, and the arc check time count can increase by one every time one half cycle elapses between ZCPs.

[0082] And when the arc check time count reaches a preset time count (reference time count), that is, whether an arc has occurred can be determined based on the estimated number of arc occurrences during the elapse of a preset number of half cycles. Accordingly, the arc check time count may be a time count for determining whether the reference time for determining whether an arc has occurred has expired when an arc occurrence is estimated.

[0083] In the above step S500, when the current offset operation and arc check time count are increased, the control unit (300) can calculate the peak current based on the current signal samples collected during the half cycle (S502).

[0084] Here, the peak current may be a current whose size is greater than or equal to a certain level among the currents detected during the half cycle, as described in (b) of the above-described FIG. 4 (e.g., current in the arc conduction step (413, 423)). In this case, the control unit (300) may calculate the peak current by calculating the root mean square (e.g., RMS) of the current values ​​of current signals whose sizes are greater than or equal to a certain level among the samples of current signals collected during the half cycle.

[0085] In the above step S502, when the peak current is calculated, the control unit (300) can set a reference count according to the size of the calculated peak current (S504). The reference count may be a reference value for determining whether an arc has occurred based on the estimated number of arc occurrences during a reference time when an arc occurrence is estimated.

[0086] The higher the reference value, the more arc occurrences must be estimated before an arc can be identified. Therefore, the higher the reference value, the more precisely the arc occurrence can be identified. On the other hand, if the reference value is lower, the arc occurrence can be identified even when the arc occurrence is estimated to be low, so the arc occurrence can be identified within a shorter period of time.

[0087] Here, the greater the magnitude of the peak current, the higher the probability of a strong arc occurring, and the greater the strength of the arc, the higher the risk of safety accidents such as electrical fires. Therefore, the greater the magnitude of the peak current, the more necessary it is to quickly identify and block the occurrence of an arc. Therefore, the larger the magnitude of the peak current, the lower the reference count can be set so that an arc can be identified even when the estimated number of arc occurrences is small.

[0088] On the other hand, the smaller the peak current, the higher the probability that the arc will not be large. Furthermore, a smaller arc strength may lower the risk of safety accidents due to arc occurrence. Conversely, if the circuit between the power source and the load is interrupted, the power supply to the load may be cut off, preventing the load from operating, which may result in damage. Accordingly, the smaller the peak current, the more accurately the occurrence of an arc needs to be determined. Therefore, the smaller the peak current, the higher the reference count can be set.

[0089] Therefore, the control unit (300) can adaptively set the size of the reference count according to the size of the peak current calculated in the step S502. Preferably, the control unit (300) can set the size of the reference count to '3' when the size of the peak current calculated in the step S502 is 150 A or more, and can set the size of the reference count to '4' when it is 100 A or more and less than 150 A. In addition, the size of the reference count can be set to '5' when it is 75 A or more and less than 100 A, and can set the size of the reference count to '6' when it is less than 75 A.

[0090] In this case, if the reference count is 3, it means that there are three half-cycles in which an arc is estimated to have occurred within the reference time according to the arc check time count, and if the reference count is 6, it can mean that there are six half-cycles in which an arc is estimated to have occurred within the reference time according to the arc check time count. That is, if the reference count is 3 or 6, it can be determined that an arc has occurred if three or six half-cycles in which an arc is estimated to have occurred are detected within the reference time.

[0091] Meanwhile, when the reference count is determined in step S504, the control unit (300) can check whether the peak current calculated in step S502 exceeds the preset reference current (S506).

[0092] And as a result of the check in step S506, if the peak current does not exceed the preset reference current, the control unit (300) may estimate that no arc occurred during the half cycle and may check whether the arc check time count has reached the preset reference time count (S518). Preferably, the reference time count may be set to 60. In this case, when the frequency of the AC current is 60 Hz and the reference time count is set to 60, the time corresponding to 60 half cycles (between ZCPs), that is, the time when the reference time count expires, may be a time corresponding to 0.5 seconds.

[0093] As described above, since the reference time count increases with each half cycle, when the frequency of the AC current is higher, the time corresponding to the reference time count may be shorter even if the reference time count is the same. On the other hand, when the frequency of the AC current is lower, the time corresponding to the reference time count may be longer even if the reference time count is the same.

[0094] On the other hand, if the peak current calculated as a result of the check in step S506 exceeds the preset reference current, the control unit (300) can calculate the average value of the high-frequency noise signal samples collected during the half cycle (S508). Then, it can be checked whether the average value of the calculated high-frequency noise signal samples exceeds the preset reference value (S510). Here, the reference value may be a reference value for estimating whether an arc has occurred based on the average value of the high-frequency noise signal samples.

[0095] If the average intensity of the high-frequency noise signal during the half cycle does not exceed the preset reference value as a result of the check in step S510, the control unit (300) can estimate that no arc occurred during the half cycle. Accordingly, the process can proceed to step S518 to check whether the arc check time count has reached the preset reference time count.

[0096] On the other hand, if the average intensity of the high-frequency noise signal collected during the half cycle exceeds a preset reference value as a result of the determination in step S510, the control unit (300) can estimate that an arc occurred during the half cycle. That is, if the average intensity of the high-frequency noise signal during the half cycle exceeds a preset reference value while the peak current during the half cycle exceeds the reference current value, the control unit (300) can estimate that an arc occurred during the half cycle in which the current signal sample and the high-frequency noise signal sample were collected.

[0097] Then, the control unit (300) can increase the arc count according to the arc occurrence estimation (e.g., increase the arc count value by 1) (S512). Then, it can check whether the arc count counted up to now has reached a preset reference count, i.e., whether it is greater than or equal to the preset reference count (S514). Here, the reference count may be a reference count determined according to the peak current in the S514 step.

[0098] As a result of the check in step S514, if the estimated number of arc occurrences counted so far, i.e., the arc count, is less than the reference count determined according to the peak current, the control unit (300) may proceed to step S518 to check whether the arc check time count has reached the preset reference time count.

[0099] However, if the arc count counted so far is greater than the determined reference count as a result of the check in step S514, the control unit (300) can determine that an arc has occurred. Accordingly, a trip control signal can be transmitted to the cutoff unit (350) to cut off the load from the power source (S516). Then, according to the operation of the cutoff unit (350), the circuit between the power source and the load can be opened, thereby cutting off the power supply to the load.

[0100] Meanwhile, if the peak current is lower than the reference current in step S506, or if the average intensity of high-frequency noise is lower than the reference value in step S510, or if the arc count counted up to now is lower than the reference count, the control unit (300) can proceed to step S518 to check whether the arc check time count has reached the preset reference time count.

[0101] If, as a result of the check in step S518, the arc check time count increased to date has not reached the preset reference time count, the control unit (300) may proceed to step S500 again to perform a current offset operation and increase the arc check time count. That is, while the arc check time count is counted to date, the arc check time count may be increased by 1 and the processes below step S500 may be performed again.

[0102] On the other hand, if the result of the check in step S518 indicates that the arc check time count increased to date has reached a preset reference time count, the control unit (300) can initialize the arc check time count counted to date (S520). For example, if the reference time count is set to 60, the arc check time count can be initialized to 0 through steps S518 and S520 when the arc check time count increased to date reaches 60.

[0103] And the control unit (300) can reset the arc counts checked before the reference time count among the arc counts checked up to now (S522). Accordingly, among the arc counts counted up to now, the arc counts counted before the reference time count (e.g., 60) are initialized, so that the number of arc counts counted up to now can be reduced.

[0104] For example, if the arc count is counted when the arc check time count is 50, the arc check time count may be reset to 0 again when the arc check time count reaches 60. However, the arc count may remain in a state where it is counted as 1.

[0105] And when the arc check time count becomes 20 again, the arc count can be increased to 2 if the arc count is counted. Also, when the arc check time count becomes 59, the arc count can be increased to 3 if the arc count is counted. In this state, when the arc check time count becomes 60 again, the arc check time count can be initialized to 0 again.

[0106] However, in this case, among the arc counts counted up to now, the first counted arc count may be the arc count counted before 60 arc check time counts (reference time count) from the time when the arc check time count is initialized to 0. In the above example, the first arc count may be the arc count counted before the time corresponding to 70 arc check time counts. Accordingly, the control unit (300) may initialize the arc count that occurred before the reference time count among the arc counts counted up to now in the step S522.

[0107] That is, as the first arc count is initialized, the arc count can be decreased from 3 to 2. Then, the control unit (300) can proceed to step S500 again in a state where the arc count counted before the reference time count is initialized, perform a current offset operation, and increase the arc check time count. That is, in a state where some of the arc counts are initialized and the remaining arc counts are maintained, the arc check time count can be increased by 1, and the processes below step S500 can be performed again.

[0108] To this end, the control unit (300) can store information on the arc check time count corresponding to the counted arc count in the memory (370) each time the arc count is counted.

[0109] Therefore, the arc monitoring device according to an embodiment of the present invention can estimate that an arc has occurred when the peak current calculated during a half cycle exceeds a preset reference current, and the average intensity value of the high-frequency noise signal collected during the half cycle exceeds a reference value. In addition, when the estimated number of arc occurrences is greater than or equal to the reference count calculated according to the peak current during a reference time (a time determined according to the arc check time count), it can determine that an arc has occurred and disconnect the load from the power source. In this case, the present invention can increase the arc determination accuracy by increasing the value of the reference count as the peak current is smaller, and can increase the arc determination speed more quickly by decreasing the value of the reference count as the peak current is larger.

[0110] The present invention described above can be implemented as computer-readable code on a medium having a program recorded thereon. Computer-readable media include 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 include media implemented in the form of carrier waves (e.g., transmission via the Internet). Therefore, the above detailed description should not be construed as limiting in any respect, but rather 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. A high-frequency signal detection unit that detects a high-frequency signal from the current flowing in the circuit; A circuit breaker that blocks the electrical connection between the power source and the load by blocking the above circuit; A voltage detection unit that detects a voltage change in the above circuit; A current detection unit that detects a change in current in the above circuit; and An arc monitoring device characterized by comprising a control unit that detects a zero crossing point, which is a point in time having a reference voltage according to a phase alternation of the voltage from the voltage change, and estimates whether an arc has occurred during the half cycle based on the average of the current magnitude detected during the half cycle of the current corresponding to the detected zero crossing point and the intensity of the high-frequency signal between the zero crossing points, and determines whether an arc has occurred in the circuit based on whether the estimated number of arc occurrences is greater than or equal to a preset reference number, and controls the blocking unit to block the circuit based on the determination result.

2. In paragraph 1, The above control unit, The reference number of times is determined based on the current size detected during the above half cycle, The above criteria number is, An arc monitoring device characterized in that the larger the detected current size, the smaller the value determined.

3. In paragraph 1, the control unit, An arc monitoring device characterized in that it performs a current offset operation on current signals sampled during the above half cycle and calculates an effective value for current signals in which a current greater than a certain size is detected, thereby calculating the current size.

4. In paragraph 1, the control unit, An arc monitoring device characterized in that it is determined whether an arc has occurred in the circuit based on whether the estimated number of times the arc has occurred during the time period in which the above half-cycle is repeated a preset number of times is greater than or equal to the reference number.

5. In paragraph 4, the control unit, An arc monitoring device characterized in that, if the estimated number of arc occurrences during the time period in which the half-cycle is repeated a preset number of times is less than the reference number, the estimated number of arc occurrences counted before the time period in which the half-cycle is repeated a preset number of times is deducted from the estimated number of arc occurrences counted so far.

6. In paragraph 1, The above arc monitoring device, It is further equipped with a ZCT (Zero-phase Current Transformer) to detect leakage current, The above control unit, An arc monitoring device characterized in that it further determines whether a leakage current occurs in the circuit based on the detection result of the ZCT and further controls the circuit breaker based on the determination result.

7. In the first paragraph, the control unit, An arc monitoring device characterized in that the zero crossing point detected according to the voltage change of the voltage detection unit is input as an interrupt signal, and sampling of a current signal and a high-frequency signal begins when the interrupt signal is received.

8. In paragraph 1, The above high frequency signal detection unit, It is formed by including an HFCT (High Frequency Current Transformer) and an HPF (High Pass Filter) formed to allow only high-frequency signals above a preset frequency band to pass through. The above current detection unit, An arc monitoring device characterized in that it is formed by including at least one of a shunt resistor and a low frequency current transformer (LFCT).

9. The first step is to detect the zero crossing point, which is the point in time when the reference voltage is reached according to the voltage change of the current flowing in the circuit; A second step of sampling the current signal and high-frequency signal during a half cycle of the current between the detected zero crossing point and the zero crossing point when the zero crossing point is detected; A third step is to increment the arc check time count to check the elapsed time; A fourth step of calculating the average value of the current signal size and high-frequency signal during the above half cycle; A fifth step of estimating whether an arc occurred during the half cycle in which the current signal and the high frequency signal were sampled based on the magnitude of the generated current signal and the average value of the high frequency signal; A sixth step of increasing the estimated number of arc occurrences when arc occurrence is estimated and checking whether the number of arc occurrences accumulated to date is greater than or equal to the reference count; A seventh step of cutting off the electrical connection between the power source and the load by cutting off the circuit when the number of accumulated arc occurrences is greater than or equal to the reference count; An eighth step of checking whether the accumulated arc check time count has reached a preset reference time count when an arc occurrence is not estimated in the fifth step or the accumulated number of arc occurrences in the sixth step is less than a reference count; A ninth step of performing the first step and the steps after the first step again if the accumulated arc check time count does not reach the reference time count; and A control method for an arc monitoring device, characterized in that it comprises a 10th step of initializing the accumulated arc check time count when the accumulated arc check time count reaches the reference time count and performing the first step and the steps after the first step again.

10. In paragraph 9, The above 10th step is, It further includes a step 10-1 of deducting the number of times counted before a preset time from the above accumulated number of arc occurrences, The above preset time is, A control method of an arc monitoring device characterized in that the time corresponding to the case where the above half cycle is repeated as many times as the number of the above reference time count.

11. In paragraph 10, the preset time is: A control method of an arc monitoring device, characterized in that the preset time is 0.5 seconds when the reference time count and the frequency of the current flowing in the circuit are the same, and the preset time is determined according to the frequency of the current flowing in the circuit.

12. In paragraph 9, the fourth step is, Step 4-1 of performing a current offset operation on current signals sampled during the above half cycle; and A control method for an arc monitoring device, characterized in that it includes a step 4-2 of calculating the size of the current signal by calculating the root mean square (RMS) value for current signals in which a current greater than a certain size is detected as a result of the current offset operation.

13. In the 12th paragraph, the fourth step is Further comprising a step 4-3 of determining the reference count based on the current size detected during the above half cycle, The above reference count is, A control method for an arc monitoring device, characterized in that the larger the detected current size, the smaller the current is determined.

14. In paragraph 9, the fifth step is, Step 5-1 of comparing the size of the above-mentioned generated current signal with a preset reference current; Step 5-2 of calculating the average value of the high-frequency signal when the magnitude of the generated current signal exceeds the preset reference current; Step 5-3 proceeds to step 8, which checks whether the accumulated arc check time count has reached the preset reference time count when the size of the generated current signal is less than the preset reference current; Step 5-4 of estimating whether an arc occurred during the half cycle in which the current signal and the high frequency signal were sampled if the average value of the generated high frequency signal exceeds a preset reference value; and A control method for an arc monitoring device, characterized in that it includes a step 5-5, which proceeds to the eighth step of checking whether the accumulated arc check time count has reached the preset reference time count when the average value of the high-frequency signal produced above is less than the preset reference value.

15. In paragraph 9, the high frequency signal is A control method for an arc monitoring device characterized by being a high-frequency noise signal detected through an HFCT (High Frequency Current Transformer) and an HPF (High Pass Filter) formed to allow only high-frequency signals above a preset frequency band to pass.

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