Electrical circuit monitoring method, program, and electrical circuit monitoring system

Abstract

To reduce a likelihood that an electrical leakage breaker will falsely detect the occurrence of an electrical leakage based on a monitoring signal.SOLUTION: An electrical line monitoring system 1 comprises a signal input device 2 and a signal extraction device 3. The signal input device 2 inputs a monitoring signal to an electrical line for electric power distribution. The signal extraction device 3 extracts a monitoring signal from the electrical line. The signal input device 2 intermittently inputs signals of a higher frequency than the commercial frequency into the electrical line as a monitoring signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure generally relates to circuit monitoring methods, programs, and circuit monitoring systems. More specifically, this disclosure relates to a circuit monitoring system that inputs a monitoring signal to a circuit, a circuit monitoring method that includes the step of inputting a monitoring signal to a circuit, and a program that implements the circuit monitoring method. [Background technology]

[0002] The circuit monitoring system disclosed herein can be used, for example, as a ground fault circuit breaker. Patent Document 1 discloses a ground fault circuit breaker. The ground fault circuit breaker detects unbalanced currents flowing through multiple circuits using a zero-phase current transformer and detects the occurrence of a ground fault when the magnitude of the unbalanced current exceeds an upper limit. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2003-7191 [Overview of the project] [Problems that the invention aims to solve]

[0004] When the circuit monitoring system (first leakage circuit breaker) inputs a monitoring signal to the circuit, another (second) leakage circuit breaker may mistakenly detect the occurrence of a leakage current based on the monitoring signal.

[0005] This disclosure aims to provide a circuit monitoring method, program, and circuit monitoring system that can reduce the possibility of a (second) leakage circuit breaker falsely detecting the occurrence of a leakage current based on a monitoring signal. [Means for solving the problem]

[0006] A circuit monitoring method according to an aspect of the present disclosure includes a signal input step and a signal extraction step. In the signal input step, a monitoring signal is input to a power distribution circuit. In the signal extraction step, the monitoring signal is extracted from the circuit. In the signal input step, an alternating current signal having a frequency higher than the commercial frequency is intermittently input to the circuit as the monitoring signal. In the signal input step, a plurality of AC signals, each of which is a monitoring signal, are periodically switched and input to the circuit. The plurality of AC signals have different frequencies. A circuit monitoring method according to one aspect of this disclosure includes a signal input step and a signal extraction step. In the signal input step, a monitoring signal is input to a power distribution circuit. In the signal extraction step, the monitoring signal is extracted from the circuit. In the signal input step, an AC signal with a frequency higher than the commercial frequency is intermittently input to the circuit as the monitoring signal. The monitoring signal is a signal corresponding to a portion of a sinusoidal signal that is between half a period and one period. A circuit monitoring method according to one aspect of the present disclosure includes a signal input step and a signal extraction step. In the signal input step, a monitoring signal is input to a power distribution circuit. In the signal extraction step, the monitoring signal is extracted from the circuit. In the signal input step, an AC signal with a frequency higher than the commercial frequency is intermittently input to the circuit as the monitoring signal. In the signal input step, the monitoring signal is input to the circuit intermittently at intervals longer than the generation time of the monitoring signal. A circuit monitoring method according to one aspect of the present disclosure includes a signal input step and a signal extraction step. In the signal input step, a monitoring signal is input to a power distribution circuit. In the signal extraction step, the monitoring signal is extracted from the circuit. In the signal input step, an AC signal with a frequency higher than the commercial frequency is intermittently input to the circuit as the monitoring signal. In the signal input step, the monitoring signal is input to the circuit intermittently at intervals of 40 milliseconds or more. A circuit monitoring method according to one aspect of the present disclosure includes a signal input step and a signal extraction step. In the signal input step, a monitoring signal is input to a power distribution circuit. In the signal extraction step, the monitoring signal is extracted from the circuit. In the signal input step, an AC signal with a frequency higher than the commercial frequency is intermittently input to the circuit as the monitoring signal. In the signal input step, the monitoring signal is input to the circuit intermittently at intervals of four times or less the generation time of the monitoring signal. A circuit monitoring method according to one aspect of the present disclosure includes a signal input step and a signal extraction step. In the signal input step, a monitoring signal is input to a power distribution circuit. In the signal extraction step, the monitoring signal is extracted from the circuit. In the signal input step, an AC signal with a frequency higher than the commercial frequency is intermittently input to the circuit as the monitoring signal. The frequency of the monitoring signal is lower than the carrier frequency of an inverter electrically connected to the circuit.

[0007] A program according to an aspect of the present disclosure is a program for causing one or more processors of a computer system to execute the circuit monitoring method.

[0008] A circuit monitoring system according to an aspect of the present disclosure includes a signal input device and a signal extraction device. The signal input device inputs a monitoring signal to a power distribution circuit. The signal extraction device extracts the monitoring signal from the circuit. The signal input device intermittently inputs a signal having a frequency higher than the commercial frequency to the circuit as the monitoring signal. The signal input device periodically switches between a plurality of AC signals, each of which is a monitoring signal, and inputs them to the circuit. The plurality of AC signals have different frequencies. A circuit monitoring system according to one aspect of this disclosure comprises a signal input device and a signal extraction device. The signal input device inputs a monitoring signal to a power distribution circuit. The signal extraction device extracts the monitoring signal from the circuit. The signal input device intermittently inputs a signal with a frequency higher than the commercial frequency to the circuit as the monitoring signal. The monitoring signal is a signal corresponding to a portion of a sinusoidal signal that is between half a period and one period. A circuit monitoring system according to one aspect of the present disclosure comprises a signal input device and a signal extraction device. The signal input device inputs a monitoring signal to a power distribution circuit. The signal extraction device extracts the monitoring signal from the circuit. The signal input device intermittently inputs a signal with a frequency higher than the commercial frequency as the monitoring signal to the circuit. The signal input device intermittently inputs the monitoring signal to the circuit at intervals longer than the generation time of the monitoring signal. A circuit monitoring system according to one aspect of this disclosure comprises a signal input device and a signal extraction device. The signal input device inputs a monitoring signal to a power distribution circuit. The signal extraction device extracts the monitoring signal from the circuit. The signal input device intermittently inputs a signal with a frequency higher than the commercial frequency to the circuit as the monitoring signal. The signal input device intermittently inputs the monitoring signal to the circuit at intervals of 40 milliseconds or more. A circuit monitoring system according to one aspect of this disclosure comprises a signal input device and a signal extraction device. The signal input device inputs a monitoring signal to a power distribution circuit. The signal extraction device extracts the monitoring signal from the circuit. The signal input device intermittently inputs a signal with a frequency higher than the commercial frequency as the monitoring signal to the circuit. The signal input device intermittently inputs the monitoring signal to the circuit at intervals of four times or less the generation time of the monitoring signal. A circuit monitoring system according to one aspect of this disclosure comprises a signal input device and a signal extraction device. The signal input device inputs a monitoring signal to a power distribution circuit. The signal extraction device extracts the monitoring signal from the circuit. The signal input device intermittently inputs a signal with a frequency higher than the commercial frequency to the circuit as the monitoring signal. The frequency of the monitoring signal is lower than the carrier frequency of an inverter electrically connected to the circuit.

Advantages of the Invention

[0009] The present disclosure has an advantage of being able to reduce the possibility that a leakage breaker erroneously detects the occurrence of leakage based on a monitoring signal.

Brief Description of the Drawings

[0010] [Figure 1] FIG. 1 is a block diagram of a power system including a circuit monitoring system according to an embodiment. [Figure 2] Figure 2 is a block diagram of the signal input device for the same circuit monitoring system. [Figure 3] Figure 3A is a perspective view of the current transformer of the signal extraction device for the same circuit monitoring system, installed in the circuit. Figure 3B is a perspective view of the same system before the current transformer is installed in the circuit. [Figure 4] Figure 4 shows the waveform of the signal input by the same circuit monitoring system. [Figure 5] Figure 5 is a waveform diagram showing the current waveform detected by a ground fault circuit breaker when a ground fault occurs in the electrical circuit. [Figure 6] Figure 6 is a waveform diagram showing the current waveform detected by a ground fault circuit breaker when a lightning surge occurs in the electrical circuit. [Modes for carrying out the invention]

[0011] (Embodiment) The following describes the circuit monitoring method, program, and circuit monitoring system 1 according to the embodiments, with reference to the drawings. However, the embodiments described below are only one of many embodiments of this disclosure. The embodiments described below can be modified in various ways depending on the design, etc., as long as the objectives of this disclosure are achieved. In addition, the figures described in the embodiments below are schematic diagrams, and the ratios of the size and thickness of each component in the figures do not necessarily reflect the actual dimensional ratios.

[0012] (overview) Figure 1 shows the circuit monitoring system 1 of this embodiment and several related configurations. The circuit monitoring system 1 is installed, for example, in a factory, apartment building, hospital, or mixed-use commercial facility. The circuit monitoring system 1 is installed to monitor the circuit that supplies power from the commercial power source to the load 201.

[0013] The circuit monitoring system 1 comprises a signal input device 2 and a signal extraction device 3. The signal input device 2 inputs a monitoring signal to the power distribution circuit. The signal extraction device 3 extracts the monitoring signal from the circuit. The signal input device 2 intermittently inputs a signal with a frequency higher than the commercial frequency to the circuit as a monitoring signal.

[0014] According to the circuit monitoring system 1 of this embodiment, the signal input device 2 that generates the monitoring signal can be miniaturized compared to cases where the monitoring signal is a DC signal or an AC signal with a frequency lower than the commercial frequency (details will be described later). Furthermore, when a ground fault circuit breaker 81 is installed in the circuit, the possibility of the ground fault circuit breaker 81 falsely detecting the occurrence of a ground fault based on the monitoring signal can be reduced (details will be described later). Of course, the circuit monitoring system 1 may also be installed even if a ground fault circuit breaker 81 is not installed in the circuit.

[0015] Furthermore, the circuit monitoring system 1 can detect the occurrence of electrical leakage in the circuit based on the monitoring signal extracted by the signal extraction device 3. For example, if the resistance component of the AC current used as the monitoring signal exceeds a threshold, the circuit monitoring system 1 determines that electrical leakage has occurred in the circuit.

[0016] Furthermore, the same functions as the circuit monitoring system 1 can be realized by a circuit monitoring method. The circuit monitoring method of this embodiment includes a signal input step and a signal extraction step. In the signal input step, a monitoring signal is input to the power distribution circuit. In the signal extraction step, a monitoring signal is extracted from the circuit. In the signal input step, an AC signal with a frequency higher than the commercial frequency is intermittently input to the circuit as a monitoring signal.

[0017] Furthermore, the circuit monitoring method can be implemented using a program. The program in this embodiment is a program that causes one or more processors in a computer system to execute the circuit monitoring method. The program may be recorded on a non-temporary recording medium that is readable by the computer system.

[0018] (detail) (1) Overall structure Hereinafter, the circuit monitoring system 1 and several related components will be collectively referred to as the power system 100. As shown in Figure 1, the power system 100 comprises a signal input device 2, a monitoring device 9, power receiving equipment 7, and several (two in Figure 1) distribution boards 8. The power receiving equipment 7 has a transformer 71 and several (two in Figure 1) feeders 72. Each of the multiple distribution boards 8 has a signal extraction device 3, a main circuit breaker 80, and several (two in Figure 1) branch circuit breakers 82. Each of the multiple branch circuit breakers 82 is electrically connected to a load 201. The power system 100 also includes a circuit that electrically connects the commercial power source and the load 201. The transformer 71, feeders 72, main circuit breaker 80, and multiple branch circuit breakers 82 each include a part of the above circuit. The above circuit also includes a first circuit 4, a second circuit 5, and a third circuit 6. The first circuit 4, the second circuit 5, and the third circuit 6 constitute the power system 100.

[0019] Furthermore, the power system 100 includes a circuit monitoring system 1. The circuit monitoring system 1 comprises the aforementioned signal input device 2, signal extraction device 3, and monitoring device 9.

[0020] (2) Power receiving equipment The power receiving equipment 70 is, for example, a cubicle-type high-voltage power receiving equipment. The power receiving equipment 70 has a transformer 71. The transformer 71 includes a primary winding 711 and a secondary winding 712. An AC voltage V0 of 6600V (RMS) transmitted from the commercial power source is applied to the primary winding 711 of the transformer 71. The transformer 71 transforms the AC voltage V0 of 6600V applied to the primary winding 711 into an AC voltage of 200V (RMS) applied to the secondary winding 712, for example. In this embodiment, the AC voltage V0 received by the power receiving equipment 70 is a single-phase AC voltage, but it may also be a three-phase AC voltage.

[0021] The secondary winding 712 is electrically connected to the first circuit 4. The first circuit 4 is the circuit between the secondary winding 712 and the multiple feeders 72. The first circuit 4 includes a neutral wire 40, a first voltage line 41, and a second voltage line 42. The first circuit 4 further includes neutral wires 40A and 40B branched from the neutral wire 40, first voltage lines 41A and 41B branched from the first voltage line 41, and second voltage lines 42A and 42B branched from the second voltage line 42.

[0022] An intermediate tap 713 is provided on the secondary winding 712. The intermediate tap 713 is electrically connected to the neutral wire 40. The neutral wire 40 is grounded via a grounding wire 44.

[0023] The first end of the secondary winding 712 is electrically connected to the first voltage line 41. The second end of the secondary winding 712 is electrically connected to the second voltage line 42.

[0024] A 100V AC voltage V11 (the potential of the first voltage line 41 relative to the potential of the neutral line 40) is applied between the first voltage line 41 and the neutral line 40. A 100V AC voltage V12 (the potential of the neutral line 40 relative to the potential of the second voltage line 42) which is in phase with the AC voltage V11 is applied between the second voltage line 42 and the neutral line 40. Therefore, a 200V AC voltage is applied between the first voltage line 41 and the second voltage line 42.

[0025] The neutral wire 40 branches into two neutral wires 40A and 40B. The first voltage wire 41 branches into two first voltage wires 41A and 41B. The second voltage wire 42 branches into two second voltage wires 42A and 42B. The neutral wire 40, the first voltage wire 41 and the second voltage wire 42 are electrically connected to one feeder 72 via the neutral wire 40A, the first voltage wire 41A and the second voltage wire 42A. The neutral wire 40, the first voltage wire 41 and the second voltage wire 42 are electrically connected to another feeder 72 via the neutral wire 40B, the first voltage wire 41B and the second voltage wire 42B.

[0026] Furthermore, the number of circuits branched from each of the neutral wire 40, the first voltage line 41, and the second voltage line 42 is not limited to two, but may be three or more. Also, the neutral wire 40, the first voltage line 41, and the second voltage line 42 may be electrically connected to a single feeder 72 without branching.

[0027] Each of the multiple feeders 72 electrically connects the first circuit 4 and the second circuit 5, and protects the connection point.

[0028] A second circuit 5 is provided on the secondary side of each of the multiple feeders 72. In this embodiment, the configuration of the secondary side of each feeder 72 is the same regardless of which feeder 72 is being considered. Below, the configuration of the secondary side of one of the multiple feeders 72 will be described.

[0029] The second circuit 5 is the circuit between the feeder 72 and the main breaker 80. The second circuit 5 includes the neutral wire 50, the first voltage line 51, and the second voltage line 52. The second circuit 5 further includes neutral wires 50A and 50B branched from the neutral wire 50, first voltage lines 51A and 51B branched from the first voltage line 51, and second voltage lines 52A and 52B branched from the second voltage line 52.

[0030] The first circuit 4 is electrically connected to the second circuit 5 via a feeder 72. More specifically, the neutral wire 40A, the first voltage line 41A, and the second voltage line 42A are electrically connected to the neutral wire 50, the first voltage line 51, and the second voltage line 52, respectively, via a feeder 72.

[0031] The neutral wire 50 branches into two neutral wires 50A and 50B. The first voltage line 51 branches into two first voltage lines 51A and 51B. The second voltage line 52 branches into two second voltage lines 52A and 52B. The neutral wire 50, the first voltage line 51, and the second voltage line 52 are electrically connected to three primary terminals of the main breaker 80 of the distribution board 8 via the neutral wire 50A, the first voltage line 51A, and the second voltage line 52A. The neutral wire 50, the first voltage line 51, and the second voltage line 52 are electrically connected to three primary terminals of the main breaker 80 of another distribution board 8 via the neutral wire 50B, the first voltage line 51B, and the second voltage line 52B.

[0032] (3) Distribution board In this embodiment, multiple distribution boards 8 each have a similar configuration. The configuration of one distribution board 8 will be described below.

[0033] The distribution board 8 includes a signal extraction device 3, a main circuit breaker 80, and multiple (two in Figure 1) branch circuit breakers 82. The signal extraction device 3 will be explained later.

[0034] The third circuit 6 is the circuit between the main breaker 80 and the multiple branch breakers 82. The third circuit 6 includes a neutral wire 60, a first voltage line 61, and a second voltage line 62. The third circuit 6 further includes neutral wires 60A and 60B branched from the neutral wire 60, a first voltage line 61A branched from the first voltage line 61, and a second voltage line 62B branched from the second voltage line 62.

[0035] The main circuit breaker 80 has three primary terminals and three secondary terminals. The three primary terminals are electrically connected to the neutral wire 50A, the first voltage line 51A, and the second voltage line 52A. The three secondary terminals are electrically connected to the neutral wire 60, the first voltage line 61, and the second voltage line 62.

[0036] The third circuit 6 is electrically connected to the second circuit 5 via the main breaker 80. More specifically, the neutral wire 60, the first voltage line 61, and the second voltage line 62 are electrically connected to the neutral wire 50A, the first voltage line 51A, and the second voltage line 52A, respectively, via the main breaker 80.

[0037] Each of the multiple branch breakers 82 has two primary terminals and two secondary terminals. The two primary terminals are electrically connected to two of the three busbars via two branch lines. The three busbars are the neutral wire 60, the first voltage line 61, and the second voltage line 62. Focusing on branch breaker 82A, for example, the two branch lines are the neutral wire 60A and the first voltage line 61A. Focusing on branch breaker 82B, for example, the two branch lines are the neutral wire 60B and the second voltage line 62B. Alternatively, the two branch lines may be a wire branched from the first voltage line 61 and a wire branched from the second voltage line 62.

[0038] Each of the two secondary terminals of the multiple branch circuit breakers 82 is electrically connected to two wires 200 (insulated wires) for indoor wiring. A load 201 is electrically connected to these two wires 200 either directly or via an outlet such as a wall outlet. The load 201 is supplied with 100V or 200V AC power. Typical loads 201 include lighting fixtures and air conditioning equipment (air conditioners). Alternatively, for example, the two wires 200 may be electrically connected to the load 201 via an inverter 202.

[0039] Furthermore, the main circuit breaker 80 in this embodiment is a ground fault circuit breaker 81. When the ground fault circuit breaker 81 detects a ground fault, it insulates (interrupts) the connection between the primary terminal and the secondary terminal.

[0040] (4) Circuit monitoring system The circuit monitoring system 1 is an Igr-type leakage current monitoring system. The Igr-type system is a method that injects a signal into the circuit and determines the resistance component of the leakage current based on the injected signal. The circuit monitoring system 1 comprises a signal input device 2, a signal extraction device 3, and a monitoring device 9.

[0041] The signal input device 2 is preferably installed in the power receiving equipment 7. The signal input device 2 inputs a monitoring signal to the circuit via a transformer 20 located in the circuit. More specifically, the signal input device 2 inputs a monitoring signal to the grounding wire 44 of the power receiving equipment 7 via the transformer 20. The monitoring signal is an AC voltage signal with a frequency higher than the frequency (50Hz or 60Hz) of the AC voltages V11 and V12 output from the secondary side of the transformer 71. In this embodiment, the monitoring signal is a sine wave signal. The frequency of the monitoring signal is higher than 50Hz and lower than 60Hz, or higher than 60Hz. For example, the frequency of the monitoring signal is 1kHz or less.

[0042] As shown in Figure 2, the signal input device 2 includes a transformer 20, an oscillator 21, a power supply unit 22, a control unit 23, and a first communication unit 24.

[0043] The power supply unit 22 generates a DC voltage from, for example, the AC voltage V11 (or V12) output from the secondary side of the transformer 71. Preferably, the power supply unit 22 has, for example, a step-down switching power supply circuit.

[0044] The oscillator 21 includes, for example, an inverter circuit and an LC filter, and converts the DC voltage supplied from the power supply unit 22 into a sinusoidal AC voltage of a desired frequency (a frequency higher than 50 Hz or 60 Hz). The oscillator 21 applies this AC voltage as a monitoring signal to the primary winding of the transformer 20.

[0045] The transformer 20 has a ring-shaped magnetic core and a primary winding. The primary winding is wound around the ring-shaped magnetic core. A grounding wire 44 (see Figure 1) is passed through the central cavity of the ring-shaped magnetic core. When a sinusoidal AC voltage is applied from the oscillator 21 to the primary winding of the transformer 20, a sinusoidal induced voltage is induced in the grounding wire 44 that passes through the ring-shaped magnetic core of the transformer 20. In other words, a monitoring signal consisting of a sinusoidal AC voltage is input (superimposed) to the sinusoidal AC voltages V11 and V12 applied between the neutral wire 40 and the first voltage line 41, and between the neutral wire 40 and the second voltage line 42. It is preferable that the transformer 20 is a segmented type transformer.

[0046] The first communication unit 24 communicates with the second communication unit 33 of the signal extraction device 3 via a communication medium. The communication medium may be a wired communication medium such as a metal wire or optical fiber, or a wireless communication medium such as radio waves. The metal wire may be a signal line dedicated to communication or a power line. When a signal line dedicated to communication is used as the communication medium, it is preferable that the first communication unit 24 has a communication circuit compliant with serial communication standards such as RS-232C or RS-485. When a power line is used as the communication medium, it is preferable that the first communication unit 24 is configured as a PLC (Power Line Communication) modem that performs power line carrier communication. When radio waves are used as the communication medium, it is preferable that the first communication unit 24 is configured as a radio station for specified low-power radio, a wireless LAN communication device using radio waves in the 2.4GHz band or 5GHz band, or a short-range wireless communication communication device using radio waves in the 2.4GHz band or 2.45GHz band. Alternatively, the first communication unit 24 may be configured as a communication device that utilizes LPWA (Low Power Wide Area).

[0047] The control unit 23 preferably includes hardware, including a microcontroller, and software, including a program executed by the microcontroller. The control unit 23 controls the first communication unit 24 to exchange data with the signal extraction device 3.

[0048] As described above, the signal input device 2 inputs a monitoring signal to the circuit (signal input step). More specifically, in the signal input step, multiple AC signals are periodically switched and input to the circuit. Each of the multiple AC signals is a monitoring signal. The multiple AC signals have different frequencies. For example, as shown in Figure 4, in the signal input step, the signal input device 2 alternately and intermittently inputs an AC signal S1 of a first frequency and an AC signal S2 of a second frequency to the circuit.

[0049] Preferably, the AC signals S1 and S2 (monitoring signals) correspond to a portion of a sinusoidal signal that is between half a period and one period. In the example shown in Figure 4, the AC signals S1 and S2 (monitoring signals) each correspond to a portion of a sinusoidal signal that is one period. Furthermore, there is an interval T0 between the disappearance of AC signal S1 (or S2) (i.e., the current becoming 0) and the generation of the next AC signal S2 (or S1).

[0050] By increasing the interval T0 at which monitoring signals are input to a certain level or higher, the possibility of the earth leakage circuit breaker 81 installed in the circuit malfunctioning can be reduced. Figure 5 shows an example of the current waveform (instantaneous value) detected by the earth leakage circuit breaker 81 when an earth leakage occurs in the circuit connected to the earth leakage circuit breaker 81. When an earth leakage occurs, the current rises temporarily, falls, and then rises again. The earth leakage circuit breaker 81 will, for example, interrupt the circuit if the current (instantaneous value) exceeds a predetermined threshold Th1, falls below the threshold Th1, and then exceeds the threshold Th1 again within a predetermined time. Therefore, for example, if a lightning surge occurs in the circuit, even if the current exceeds the threshold Th1 only once due to the surge current, it will not exceed the threshold Th1 afterward, and the earth leakage circuit breaker 81 will not interrupt the circuit. Figure 6 shows an example of the current waveform (instantaneous value) detected by the earth leakage circuit breaker 81 when a lightning surge occurs in the circuit connected to the earth leakage circuit breaker 81.

[0051] If the monitoring signal is a continuous sinusoidal signal over several cycles, even if no leakage current occurs, the current superimposed on the monitoring signal may exceed the threshold Th1, fall below the threshold Th1, and then exceed the threshold Th1 again within a predetermined time. Therefore, the leakage circuit breaker 81 may interrupt the circuit. In contrast, by having an intermittent monitoring signal, the possibility of the leakage circuit breaker 81 mistakenly interrupting the circuit even though no leakage current has occurred can be reduced. In other words, even if the current superimposed on the monitoring signal exceeds the threshold Th1, it takes time for the current to exceed the threshold Th1 again, so the conditions for the leakage circuit breaker 81 to interrupt the circuit are not met. It is preferable that the interval T0 for inputting the monitoring signal is longer than the predetermined time mentioned above.

[0052] In the signal input step, it is preferable to intermittently input the monitoring signal to the circuit at intervals longer than the generation times T1 and T2 of the monitoring signal. In other words, it is preferable that T0 > T1 and T0 > T2 hold true. T1 is the generation time of AC signal S1, and T2 is the generation time of AC signal S2.

[0053] Furthermore, IEC standards stipulate that earth leakage circuit breakers should trip within 40 milliseconds. Therefore, in the signal input step, it is preferable to intermittently input monitoring signals to the circuit at intervals of 40 milliseconds or more. In other words, T0 is preferably 40 milliseconds or more.

[0054] Furthermore, in the signal input step, it is preferable to intermittently input the monitoring signal to the circuit at intervals of four times or less the generation time of the monitoring signal. For example, if the shorter of the generation times T1 and T2 of the monitoring signal is 12.5 milliseconds, then it is preferable that the interval T0 for inputting the monitoring signal be 12.5 × 4 = 50 milliseconds or less. It is also preferable to intermittently input the monitoring signal to the circuit at intervals of 5 minutes or less in the signal input step. By making the interval for inputting the monitoring signal relatively short, the frequency of determining whether or not there is a leakage current can be increased.

[0055] An inverter 202 (see Figure 1) may be connected to the circuit. High-frequency signals generated by the inverter 202 may reach the earth circuit breaker 81, for example, via the ground. Therefore, in order to reduce the possibility of the earth circuit breaker 81 mistakenly detecting the high-frequency signals generated by the inverter 202 as leakage current, it may be configured to filter (remove) the high-frequency components of the detection signal and detect leakage based on the filtered detection signal.

[0056] Furthermore, the high-frequency signal generated by the inverter 202 is, for example, a carrier frequency signal, and the carrier frequency is, for example, greater than 1 kHz. Therefore, in order to prevent the high-frequency signal generated by the inverter 202 and the monitoring signal from mixing, it is preferable that the frequency of the monitoring signal be 1 kHz or less. It is also preferable that the frequency of the monitoring signal be smaller than the carrier frequency of the inverter 202 that is electrically connected to the circuit.

[0057] As described above, it is preferable that the AC signals S1 and S2 (monitoring signals) are signals corresponding to a portion of a sinusoidal signal that is between half a period and one period. Here, it is said that the monitoring signal is a signal corresponding to a portion of a sinusoidal signal that is between half a period and one period, which means that the waveform of the arbitrarily injected monitoring signal has the shape of a portion of a sinusoidal signal that is between half a period and one period. For example, it is said that the monitoring signal is a signal corresponding to a portion of a sinusoidal signal that is half a wave signal, which means that the waveform of the arbitrarily injected monitoring signal is a half wave waveform. Even if the waveform of the arbitrarily injected monitoring signal is a half wave waveform, a signal with a different sign from this monitoring signal may be generated in the circuit following the arbitrarily injected monitoring signal. For example, when the monitoring signal and the signal following the monitoring signal are measured, a waveform similar to that in Figure 6 may be measured. That is, if the monitoring signal is a positive current, a negative current may be generated after the current of the monitoring signal becomes 0. In such a case as well, the monitoring signal is said to be a signal corresponding to a portion of a sinusoidal signal that is half a wave signal.

[0058] Next, the signal extraction device 3 will be described. The signal extraction device 3 is installed in each of the multiple distribution boards 8, for example, as shown in Figure 1. The signal extraction device 3 extracts monitoring signals from the second circuit 5, for example. More specifically, the signal extraction device 3 extracts monitoring signals input to the neutral line 50A, the first voltage line 51A, and the second voltage line 52A of the second circuit 5. This allows the signal extraction device 3 to monitor the insulation deterioration of the circuit relative to the ground.

[0059] The signal extraction device 3 includes a plurality of sensors 30 (three in Figure 1), a filter 31, a calculation unit 32, and a second communication unit 33.

[0060] The signal extraction device 3 extracts a monitoring signal from the electrical circuit via a sensor 30 placed in the circuit. In this embodiment, the sensor 30 is a current transformer. However, the sensor 30 may be, for example, a magnetoresistive element or a Hall element.

[0061] In the following, of the three sensors 30, the sensor 30 installed on the neutral wire 50A may be referred to as the first sensor 30A. Also, of the three sensors 30, the sensor 30 installed on the first voltage line 51A may be referred to as the second sensor 30B. Also, of the three sensors 30, the sensor 30 installed on the second voltage line 52B may be referred to as the third sensor 30C.

[0062] Sensor 30 is a split-type current transformer. As shown in Figures 3A and 3B, sensor 30 includes a first case 301, a second case 302, two wires 303 drawn out from the first case 301, a first magnetic core 304, a primary winding, a second magnetic core 305, a projection 306, and a locking piece 307.

[0063] The first case 301 is formed from, for example, a synthetic resin. The shape of the first case 301 is that of a rectangular parallelepiped. Inside the first case 301 is housed a first magnetic core 304 that is formed in a U shape. One of two electric wires 303 is electrically connected to the first end of the primary winding wound around the first magnetic core 304. The other of the two electric wires 303 is electrically connected to the second end of the primary winding. The two electric wires 303 are drawn out from the bottom surface of the first case 301. A semi-cylindrical first recess 3010 is provided on the top surface of the first case 301.

[0064] The second case 302 is formed from, for example, synthetic resin. The shape of the second case 302 is a rectangular parallelepiped. Inside the second case 302 is a second magnetic core 305, which is formed in a U shape. A semi-cylindrical second recess 3020 is provided on the top surface of the second case 302. The second case 302 is rotatably attached to the first case 301 between a closed position (see Figure 3A) in which its top surface is in contact with the top surface of the first case 301 and an open position (see Figure 3B) in which its top surface is separated from the top surface of the first case 301. A projection 306 protrudes from the side of the first case 301. A U-shaped locking piece 307 protrudes from the side of the second case 302. The first case 301 and the second case 302 are fixed in the closed position by the locking piece 307 hooking onto the projection 306 (see Figure 3A). When the first case 301 and the second case 302 are fixed in the closed position, both ends of the first magnetic core 304 and both ends of the second magnetic core 305 are magnetically coupled to form a single ring-shaped magnetic core.

[0065] With the second case 302 rotated to the open position, an electrical circuit (neutral wire 50A, first voltage line 51A, or second voltage line 52A) is inserted between the first recess 3010 of the first case 301 and the second recess 3020 of the second case 302. Then, the second case 302 is rotated from the open position to the closed position, and the locking piece 307 is hooked onto the projection 306, thereby attaching the sensor 30 to the electrical circuit. In this way, by making the sensor 30 a split-type current transformer, the sensor 30 can be easily attached to the electrical circuit.

[0066] The filter 31 includes the frequency of the monitoring signal in its passband. The input end of the filter 31 is electrically connected to the two electric wires 303 of the sensor 30. The filter 31 extracts the frequency component of the monitoring signal from the output current of the sensor 30.

[0067] The current containing the frequency component of the monitoring signal extracted by the filter 31 is converted into a voltage signal having a voltage of a magnitude corresponding to the current value and input to the arithmetic unit 32.

[0068] The arithmetic unit 32 preferably includes hardware including a microcontroller and software including a program executed by the microcontroller. The arithmetic unit 32 performs A / D conversion on the analog signal input from the filter 31 into a digital signal (extracted data) and stores it in a memory included in the hardware. The arithmetic unit 32 executes an operation for detecting a leakage current (ground fault current) flowing from the electric circuit to the ground based on the extracted data stored in the memory.

[0069] Taking the AC signals S1 and S2 as current signals, let the frequency of the AC signal S1 be f and the frequency of the AC signal S2 be xf (x>0, x≠1). Let the current values of the AC signals S1 and S2 be I f , I xf respectively. Here, I f , I xf are vectors having a resistance component and a capacitance component respectively. Let the resistance components of I f , I xf be I R , I R respectively. Since the capacitance component is proportional to the frequency, let the capacitance components of I f , I xf be I c , xI C respectively. Then, [Equation 1], [Equation 2] hold.

[0070] [Equation 1] I f 2 = I R 2 + Ic 2 [Math 2] I xf 2 = I R 2 + (xI c ) 2 Therefore, [Equation 3] holds true.

[0071] [Math 3] I xf 2 - I f 2 = (x 2 - 1) I c 2 Therefore, [Number 4] and [Number 5] hold true.

[0072] [Math 4] I c 2 = (I xf 2 - I f 2 ) / (x 2 - 1) [Number 5] I R 2 = (x 2 I f 2 - I xf 2 ) / (x 2 - 1)

[0073] In other words, using the AC signals S1 and S2 extracted by the signal extraction device 3, the calculation unit 32 can calculate the current corresponding to the resistive component of the leakage current of the circuit (hereinafter also referred to as the "detected leakage current value") from [Equation 5]. The detected leakage current value is, for example, a value proportional to the resistive component of the leakage current. Thus, the circuit monitoring method has a calculation step of calculating the current corresponding to the resistive component of the leakage current flowing between the circuit and the ground based on a plurality of AC signals S1 and S2. Furthermore, the calculation unit 32 can calculate the current corresponding to the capacitive component of the leakage current of the circuit from [Equation 4].

[0074] The calculation unit 32 determines, for example, that a leakage current has occurred in the circuit when the detected value (effective value) of the leakage current exceeds a threshold. The threshold is stored, for example, in the memory (storage device) of the calculation unit 32.

[0075] The higher the frequency of the monitoring signal, the greater the influence of the capacitive component of the leakage current. Therefore, the circuit monitoring system 1 separates the capacitive component from the resistive component through calculation, enabling it to determine the occurrence of leakage current based on the resistive component. This improves the accuracy of the determination.

[0076] The second communication unit 33 communicates with the signal input device 2 and the monitoring device 9 via a communication medium. The second communication unit 33 outputs, for example, the result of the calculation unit 32's determination of whether or not there is a ground fault.

[0077] The monitoring device 9 is, for example, an alarm or a display device for the user to monitor the occurrence of electrical leakage. As shown in Figure 1, the monitoring device 9 has a third communication unit 91, a storage unit 92, and a notification unit 93.

[0078] The third communication unit 91 communicates with the signal extraction device 3 via a communication medium.

[0079] The storage unit 92 is a storage device composed of a hard disk drive (HDD) or a solid-state drive (SSD), etc. The storage unit 92 stores the information acquired by the third communication unit 91 from the signal extraction device 3.

[0080] The notification unit 93 notifies the user of information acquired by the third communication unit 91 from the signal extraction device 3. The notification unit 93 has a light source, such as a light-emitting diode, and notifies the user of information by controlling the lighting state of the light source. Alternatively, the notification unit 93 has a display for displaying information. Alternatively, the notification unit 93 has an audio device, such as a buzzer or speaker, and notifies the user of information by sound.

[0081] The notification unit 93 may, for example, notify whether or not there is a ground fault, or it may notify the magnitude of the leakage current.

[0082] Furthermore, if the calculation unit 32 detects the occurrence of a ground fault, the circuit monitoring system 1 may open a switch installed in the circuit to interrupt the circuit. In other words, the circuit monitoring system 1 may be used as a ground fault circuit breaker.

[0083] (5) Arrangement of signal extraction device The three sensors 30 (current transformers) of the signal extraction device 3 are not limited to being installed on the neutral line 50A, the first voltage line 51A, and the second voltage line 52A. Furthermore, the signal extraction device 3 may have two or more sets of sensors 30, with each set consisting of three sensors 30, for extracting monitoring signals. Multiple signal extraction devices 3 may also be provided. Additionally, the number of sensors 30 may be one or more.

[0084] Furthermore, the sensor 30 can be placed at various locations within the electrical circuit where leakage current is to be detected. In Figure 1, the locations indicated by dashed circles P are examples of locations where the sensor 30 may be placed. That is, the sensor 30 may be placed in one, two, or all of the first electrical circuit 4, the second electrical circuit 5, and the third electrical circuit 6, for example.

[0085] Specifically, the sensor 30 may be placed, for example, on the neutral wire 40A, the first voltage line 41A, and the second voltage line 42A. Alternatively, the sensor 30 may be placed, for example, on the neutral wire 40B, the first voltage line 41B, and the second voltage line 42B.

[0086] Furthermore, the sensor 30 may be placed, for example, on the neutral wire 60A and the first voltage wire 61A. Alternatively, the sensor 30 may be placed, for example, on the neutral wire 60B and the second voltage wire 62B.

[0087] The sensor 30 may also be placed, for example, on the electric wire 200.

[0088] It is not essential that the signal extraction device 3 is part of the distribution board 8. When the sensor 30 is located in the first circuit 4, the signal extraction device 3 may be part of the power receiving equipment 7. Furthermore, the signal extraction device 3 may be independent of either the distribution board 8 or the power receiving equipment 7.

[0089] Furthermore, the sensor 30 may be built into, for example, the main circuit breaker 80 or the branch circuit breaker 82.

[0090] If sensors 30 are placed in multiple locations, when a ground fault occurs, the circuit monitoring system 1 can identify the location of the ground fault by determining which sensor 30 detected the ground fault.

[0091] (6) Advantages In the circuit monitoring system 1 of this embodiment, the signal input device 2 intermittently inputs a signal with a frequency higher than the commercial frequency to the circuit as a monitoring signal. Therefore, compared to the case where the monitoring signal is a DC signal or an AC signal with a frequency lower than the commercial frequency, the signal input device 2 that generates the monitoring signal can be miniaturized. More specifically, the transformer 20 of the components of the signal input device 2 can be miniaturized. The transformer 20 has a ring-shaped magnetic core and inputs the monitoring signal to the circuit by inducing an induced voltage in the grounding wire 44 that passes through the ring-shaped magnetic core. If the voltage of the monitoring signal is V, the magnetic flux passing through the ring-shaped magnetic core is φ, and the time is t, then V = dφ / dt holds. If the magnetic flux density is B and the area of ​​the ring-shaped magnetic core is S, then φ = BS holds. The higher the frequency, the larger the change in magnetic flux φ per unit time, so even if the area S is relatively small, a voltage V at a level detectable by the signal extraction device 3 can be obtained. By miniaturizing the transformer 20, the manufacturing cost of the transformer 20 can be reduced.

[0092] Furthermore, because the transformer 20 is small, it is easy to make it a segmented transformer. By making the transformer 20 a segmented transformer, the installation work of the transformer 20 becomes simpler, for example, because it is possible to install the transformer 20 without interrupting the power supply in the circuit.

[0093] Furthermore, since the monitoring signal is input intermittently, as described above, even if a ground fault circuit breaker 81 is installed in the circuit, the possibility of the ground fault circuit breaker 81 falsely detecting the occurrence of a ground fault based on the monitoring signal can be reduced.

[0094] (Modified version of the embodiment) The following are examples of modifications of the embodiment. These modifications may be implemented by combining them as appropriate.

[0095] In the embodiment described, the case in which the circuit monitoring system 1 is introduced to high-voltage power receiving equipment was explained. In contrast, the circuit monitoring system 1 may also be introduced to low-voltage power receiving equipment.

[0096] In the embodiment described, the case in which the circuit monitoring system 1 is introduced into a single-phase three-wire circuit was explained. However, the circuit monitoring system 1 may also be introduced into circuits of other power distribution systems, for example, single-phase two-wire, three-phase three-wire, or three-phase four-wire circuits.

[0097] The location of the transformer 20 of the signal input device 2 is not limited to the first circuit 4. The transformer 20 may be located, for example, in the second circuit 5 or the third circuit 6.

[0098] It is not essential that the first circuit 4, the second circuit 5, and the third circuit 6 are branched into multiple circuits.

[0099] The calculation unit 32 may be provided in the monitoring device 9 instead of the signal extraction device 3.

[0100] The notification unit 93 may be provided in the signal extraction device 3 instead of the monitoring device 9.

[0101] The signal input device 2 may transmit communication signals to the signal extraction device 3 to inform it of the timing to start inputting the monitoring signal and the timing to end inputting the monitoring signal. These timing notifications are made by commands transmitted from the first communication unit 24 of the signal input device 2 to the second communication unit 33 of the signal extraction device 3. The signal extraction device 3 may extract the monitoring signal in synchronization with the timing indicated by the received communication signals. Specifically, the signal extraction device 3 may extract the monitoring signal during the period from when the monitoring signal input starts until when the monitoring signal input ends, that is, during the period when the monitoring signal is input, and determine the presence or absence of a ground fault based on the extracted monitoring signal. This further reduces the possibility of the signal extraction device 3 falsely detecting the occurrence of a ground fault.

[0102] The entity that executes the circuit monitoring system 1 or circuit monitoring method in this disclosure includes a computer system. The computer system mainly consists of a processor and memory as hardware. At least a part of the functions of the entity that executes the circuit monitoring system 1 or circuit monitoring method in this disclosure is realized by the processor executing a program recorded in the memory of the computer system. The program may be pre-recorded in the memory of the computer system, provided via a telecommunications line, or provided on a non-temporary recording medium such as a memory card, optical disk, or hard disk drive that can be read by the computer system. The processor of the computer system consists of one or more electronic circuits including semiconductor integrated circuits (ICs) or large-scale integrated circuits (LSIs). The integrated circuits such as ICs or LSIs referred to here are named differently depending on the degree of integration, and include integrated circuits called system LSIs, VLSIs (Very Large Scale Integration), or ULSIs (Ultra Large Scale Integration). Furthermore, FPGAs (Field-Programmable Gate Arrays) that are programmed after the manufacture of LSIs, or logic devices that allow for the reconfiguration of junction relationships or circuit compartments within LSIs, can also be used as processors. Multiple electronic circuits may be integrated onto a single chip or distributed across multiple chips. Multiple chips may be integrated onto a single device or distributed across multiple devices. The computer system referred to here includes a microcontroller having one or more processors and one or more memories. Therefore, the microcontroller also consists of one or more electronic circuits, including semiconductor integrated circuits or large-scale integrated circuits.

[0103] Furthermore, in this embodiment, multiple functions that are integrated into one device may be distributed across multiple devices. For example, the device constituting the filter 31 of the signal extraction device 3 may be provided separately from the device constituting the calculation unit 32.

[0104] Conversely, in the embodiment, at least some of the functions of the circuit monitoring system 1, which are distributed across multiple devices, may be consolidated into a single device. For example, at least a portion of the signal input device 2 and at least a portion of the signal extraction device 3 may be consolidated into a single device.

[0105] (summary) Based on the embodiments described above, the following aspects are disclosed.

[0106] The circuit monitoring method according to the first embodiment includes a signal input step and a signal extraction step. In the signal input step, a monitoring signal is input to the power distribution circuit. In the signal extraction step, a monitoring signal is extracted from the circuit. In the signal input step, an AC signal with a frequency higher than the commercial frequency is intermittently input to the circuit as the monitoring signal.

[0107] According to the above configuration, when a ground fault circuit breaker (81) is installed in the electrical circuit, the possibility of the ground fault circuit breaker (81) falsely detecting the occurrence of a ground fault based on the monitoring signal can be reduced.

[0108] Furthermore, in the circuit monitoring method according to the second embodiment, in the signal input step, a plurality of AC signals (S1, S2), each of which is a monitoring signal, are periodically switched and input to the circuit. The plurality of AC signals (S1, S2) have different frequencies.

[0109] With the above configuration, it becomes possible to separate the capacitive component from the resistive component by performing calculations using the multiple AC signals (S1, S2) extracted in the signal extraction step.

[0110] Furthermore, the circuit monitoring method according to the third embodiment further includes a calculation step in the second embodiment. In the calculation step, the current corresponding to the resistance component of the leakage current flowing between the circuit and the ground is calculated based on a plurality of AC signals (S1, S2).

[0111] According to the above configuration, by separating the capacitive component from the resistive component through calculation, it becomes possible to determine the occurrence of leakage current based on the resistive component. This improves the accuracy of the determination.

[0112] Furthermore, in the circuit monitoring method according to the fourth embodiment, in any one of the first to third embodiments, the monitoring signal is a signal corresponding to a portion of a sinusoidal signal that is between half a period and one period.

[0113] The above configuration reduces the possibility of false detection by the leakage circuit breaker (81).

[0114] Furthermore, in the circuit monitoring method according to the fifth embodiment, in any one of the first to fourth embodiments, the signal input step involves intermittently inputting a monitoring signal to the circuit at intervals longer than the generation time of the monitoring signal.

[0115] The above configuration reduces the possibility of false detection by the leakage circuit breaker (81).

[0116] Furthermore, in the circuit monitoring method according to the sixth embodiment, in any one of the first to fifth embodiments, a monitoring signal is intermittently input to the circuit at intervals of 40 milliseconds or more during the signal input step.

[0117] The above configuration reduces the possibility of false detection by the leakage circuit breaker (81).

[0118] Furthermore, in the circuit monitoring method according to the seventh embodiment, in any one of the first to sixth embodiments, the signal input step involves intermittently inputting a monitoring signal to the circuit at intervals of four times or less the generation time of the monitoring signal.

[0119] The above configuration allows for a higher frequency of determining whether or not there is a short circuit.

[0120] Furthermore, in the circuit monitoring method according to the eighth aspect, the frequency of the monitoring signal is 1 kHz or less in any one of the first to seventh aspects.

[0121] The above configuration reduces the possibility of high-frequency signals generated by the inverter (202) and monitoring signals being mixed together.

[0122] Furthermore, in the circuit monitoring method according to the ninth embodiment, in any one of the first to eighth embodiments, the frequency of the monitoring signal is smaller than the carrier frequency of the inverter (202) electrically connected to the circuit.

[0123] The above configuration reduces the possibility of high-frequency signals generated by the inverter (202) and monitoring signals being mixed together.

[0124] Configurations other than those in the first embodiment are not essential to the circuit monitoring system (1) and can be omitted as appropriate.

[0125] Furthermore, the program relating to the tenth embodiment is a program that causes one or more processors of a computer system to execute the circuit monitoring method relating to any one of the first to ninth embodiments.

[0126] According to the above configuration, when a ground fault circuit breaker (81) is installed in the electrical circuit, the possibility of the ground fault circuit breaker (81) falsely detecting the occurrence of a ground fault based on the monitoring signal can be reduced.

[0127] Furthermore, the circuit monitoring system (1) according to the 11th embodiment includes a signal input device (2) and a signal extraction device (3). The signal input device (2) inputs a monitoring signal to the power distribution circuit. The signal extraction device (3) extracts the monitoring signal from the circuit. The signal input device (2) intermittently inputs a signal with a frequency higher than the commercial frequency to the circuit as a monitoring signal.

[0128] According to the above configuration, when a ground fault circuit breaker (81) is installed in the electrical circuit, the possibility of the ground fault circuit breaker (81) falsely detecting the occurrence of a ground fault based on the monitoring signal can be reduced.

[0129] Furthermore, in the circuit monitoring system (1) according to the 12th embodiment, in the 11th embodiment, the signal input device (2) transmits a communication signal to the signal extraction device (3) that indicates the timing for inputting a monitoring signal. The signal extraction device (3) extracts the monitoring signal in synchronization with the timing indicated by the received communication signal.

[0130] The above configuration further reduces the possibility of false detection of electrical leakage.

[0131] Not limited to the above embodiments, various configurations (including modifications) of the circuit monitoring system (1) according to the embodiment can be realized by a circuit monitoring method, a (computer) program, or a non-temporary recording medium on which the program is recorded. [Explanation of symbols]

[0132] 1. Electrical Circuit Monitoring System 2. Signal input device 3 Signal extractor 202 Inverter S1, S2 AC signal

Claims

1. A signal input step that inputs a monitoring signal to the power distribution circuit, The system includes a signal extraction step of extracting the monitoring signal from the aforementioned circuit, In the aforementioned signal input step, As the monitoring signal, an AC signal with a frequency higher than the commercial frequency is intermittently input to the circuit. Multiple AC signals, each of which are the aforementioned monitoring signals, are periodically switched and input to the aforementioned circuit. The aforementioned multiple AC signals have frequencies that are different from each other. Electric circuit monitoring method.

2. A signal input step of inputting a monitoring signal to a power distribution circuit, The system includes a signal extraction step of extracting the monitoring signal from the aforementioned circuit, In the signal input step, an AC signal with a frequency higher than the commercial frequency is intermittently input to the circuit as the monitoring signal. The aforementioned monitoring signal is a signal corresponding to a portion of a sinusoidal signal that is between half a period and one period. Electric circuit monitoring method.

3. A signal input step of inputting a monitoring signal to a power distribution circuit, The system includes a signal extraction step of extracting the monitoring signal from the aforementioned circuit, In the aforementioned signal input step, As the monitoring signal, an AC signal with a frequency higher than the commercial frequency is intermittently input to the circuit. The monitoring signal is input to the circuit intermittently at intervals longer than the generation time of the monitoring signal. Electric circuit monitoring method.

4. A signal input step of inputting a monitoring signal to a power distribution circuit, The system includes a signal extraction step of extracting the monitoring signal from the aforementioned circuit, In the aforementioned signal input step, As the monitoring signal, an AC signal with a frequency higher than the commercial frequency is intermittently input to the circuit. The monitoring signal is input to the circuit intermittently at intervals of 40 milliseconds or more. Electric circuit monitoring method.

5. A signal input step of inputting a monitoring signal to a power distribution circuit, The system includes a signal extraction step of extracting the monitoring signal from the aforementioned circuit, In the aforementioned signal input step, As the monitoring signal, an AC signal with a frequency higher than the commercial frequency is intermittently input to the circuit. The monitoring signal is intermittently input to the circuit at intervals of four times or less the generation time of the monitoring signal. Electric circuit monitoring method.

6. A signal input step of inputting a monitoring signal to a power distribution circuit, The system includes a signal extraction step of extracting the monitoring signal from the aforementioned circuit, In the signal input step, an AC signal with a frequency higher than the commercial frequency is intermittently input to the circuit as the monitoring signal. The frequency of the monitoring signal is smaller than the carrier frequency of the inverter electrically connected to the circuit. Electric circuit monitoring method.

7. The claim further comprises a calculation step of calculating a current corresponding to the resistance component of the leakage current flowing between the circuit and the ground, based on the plurality of AC signals. The circuit monitoring method according to claim 1.

8. The frequency of the aforementioned monitoring signal is 1 kHz or less. The circuit monitoring method according to any one of claims 1 to 6.

9. A method for causing one or more processors of a computer system to execute the circuit monitoring method described in any one of claims 1 to 6. program.

10. A signal input device for inputting a monitoring signal to a power distribution circuit, The system includes a signal extraction device that extracts the monitoring signal from the aforementioned circuit, The aforementioned signal input device is As the monitoring signal, a signal with a frequency higher than the commercial frequency is intermittently input to the circuit. Multiple AC signals, each of which are the aforementioned monitoring signals, are periodically switched and input to the aforementioned circuit. The aforementioned multiple AC signals have frequencies that are different from each other. Electrical circuit monitoring system.

11. A signal input device that inputs monitoring signals to the power distribution circuit, The system includes a signal extraction device that extracts the monitoring signal from the aforementioned circuit, The signal input device intermittently inputs a signal with a frequency higher than the commercial frequency to the circuit as the monitoring signal. The aforementioned monitoring signal is a signal corresponding to a portion of a sinusoidal signal that is between half a period and one period. Electrical circuit monitoring system.

12. A signal input device for inputting a monitoring signal to a power distribution circuit, The system includes a signal extraction device that extracts the monitoring signal from the aforementioned circuit, The aforementioned signal input device is As the monitoring signal, a signal with a frequency higher than the commercial frequency is intermittently input to the circuit. The monitoring signal is input to the circuit intermittently at intervals longer than the generation time of the monitoring signal. Electrical circuit monitoring system.

13. A signal input device for inputting a monitoring signal to a power distribution circuit, The system includes a signal extraction device that extracts the monitoring signal from the aforementioned circuit, The aforementioned signal input device is As the monitoring signal, a signal with a frequency higher than the commercial frequency is intermittently input to the circuit. The monitoring signal is input to the circuit intermittently at intervals of 40 milliseconds or more. Electrical circuit monitoring system.

14. A signal input device for inputting a monitoring signal to a power distribution circuit, The system includes a signal extraction device that extracts the monitoring signal from the aforementioned circuit, The aforementioned signal input device is As the monitoring signal, a signal with a frequency higher than the commercial frequency is intermittently input to the circuit. The monitoring signal is intermittently input to the circuit at intervals of four times or less the generation time of the monitoring signal. Electrical circuit monitoring system.

15. A signal input device for inputting a monitoring signal to a power distribution circuit, The system includes a signal extraction device that extracts the monitoring signal from the aforementioned circuit, The signal input device intermittently inputs a signal with a frequency higher than the commercial frequency to the circuit as the monitoring signal. The frequency of the monitoring signal is smaller than the carrier frequency of the inverter electrically connected to the circuit. Electrical circuit monitoring system.

16. The signal input device transmits a communication signal to the signal extraction device to indicate the timing for inputting the monitoring signal. The signal extraction device extracts the monitoring signal in synchronization with the timing indicated by the received communication signal. The circuit monitoring system according to any one of claims 10 to 15.

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