JP2024047299A - Electrical circuit monitoring method, program, and electrical circuit monitoring system - Google Patents

Abstract

[Problem] The present disclosure aims to reduce the possibility that an earth leakage breaker will erroneously detect the occurrence of an earth leakage current based on a monitoring signal. [Solution] An electric circuit monitoring system 1 includes a signal input device 2 and a signal extraction device 3. The signal input device 2 inputs a monitoring signal to an electric circuit for power distribution. The signal extraction device 3 extracts the monitoring signal from the electric circuit. The signal input device 2 intermittently inputs a signal having a higher frequency than the commercial frequency as a monitoring signal to the electric circuit. [Selected Figure] Figure 1

Description

The present disclosure generally relates to an electric circuit monitoring method, a program, and an electric circuit monitoring system. More specifically, the present disclosure relates to an electric circuit monitoring system that inputs a monitoring signal to an electric circuit, an electric circuit monitoring method that includes a step of inputting a monitoring signal to an electric circuit, and a program that realizes the electric circuit monitoring method.

The circuit monitoring system disclosed herein is used as an earth leakage breaker, as an example. Patent Document 1 discloses an earth leakage breaker. The earth leakage breaker detects unbalanced currents flowing through multiple electric circuits using a zero-phase current transformer, and detects the occurrence of an earth leakage when the magnitude of the unbalanced current exceeds an upper limit value.

JP 2003-7191 A

When an electrical circuit monitoring system (first earth leakage breaker) inputs a monitoring signal to an electrical circuit, there is a possibility that another (second) earth leakage breaker may erroneously detect the occurrence of an electrical leakage based on the monitoring signal.

The present disclosure aims to provide an electric circuit monitoring method, program, and electric circuit monitoring system that can reduce the possibility that a (second) earth leakage breaker will erroneously detect the occurrence of an earth leakage current based on a monitoring signal.

The electric 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 an electric circuit for power distribution. In the signal extraction step, the monitoring signal is extracted from the electric circuit. In the signal input step, an AC signal having a higher frequency than the commercial frequency is intermittently input to the electric circuit as the monitoring signal.

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

An electric circuit monitoring system according to one aspect of the present disclosure includes a signal input device and a signal extraction device. The signal input device inputs a monitoring signal to an electric circuit for power distribution. The signal extraction device extracts the monitoring signal from the electric circuit. The signal input device intermittently inputs a signal having a higher frequency than the commercial frequency to the electric circuit as the monitoring signal.

The present disclosure has the advantage of reducing the possibility that an earth leakage breaker will erroneously detect the occurrence of an earth leakage current based on a monitoring signal.

FIG. 1 is a block diagram of a power system including an electric power line monitoring system according to one embodiment. FIG. 2 is a block diagram of a signal input device of the above-mentioned electrical circuit monitoring system. Fig. 3A is a perspective view of a state in which a current transformer of the signal extracting device of the electric line monitoring system is attached to an electric line, and Fig. 3B is a perspective view of the state before the current transformer is attached to the electric line. FIG. 4 is a waveform diagram of a signal input by the above-mentioned electrical circuit monitoring system. FIG. 5 is a waveform diagram showing a current waveform detected by an earth leakage breaker when an earth leakage occurs in an electric circuit. FIG. 6 is a waveform diagram showing a current waveform detected by an earth leakage breaker when a lightning surge occurs in an electric circuit.

(Embodiment)
Hereinafter, an electric circuit monitoring method, a program, and an electric circuit monitoring system 1 according to an embodiment will be described with reference to the drawings. However, the following embodiment is merely one of various embodiments of the present disclosure. The following embodiment can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. In addition, each figure described in the following embodiment is a schematic diagram, and the size and thickness ratios of each component in the figure do not necessarily reflect the actual dimensional ratios.

(overview)
1 shows an electric circuit monitoring system 1 according to the present embodiment and a number of related configurations. The electric circuit monitoring system 1 is installed in, for example, a factory, an apartment building, a hospital, a commercial complex, etc. The electric circuit monitoring system 1 is installed to monitor an electric circuit that supplies power from a commercial power source to a load 201.

The electric circuit monitoring system 1 includes a signal input device 2 and a signal extraction device 3. The signal input device 2 inputs a monitoring signal to an electric circuit for power distribution. The signal extraction device 3 extracts the monitoring signal from the electric circuit. The signal input device 2 intermittently inputs a signal having a higher frequency than the commercial frequency as a monitoring signal to the electric circuit.

According to the electric circuit monitoring system 1 of this embodiment, the signal input device 2 that generates the monitoring signal can be made smaller than when the monitoring signal is a DC signal or an AC signal with a lower frequency than the commercial frequency (details will be described later). Furthermore, when a leakage current breaker 81 is installed in the electric circuit, the possibility that the leakage current breaker 81 will erroneously detect the occurrence of a leakage current based on the monitoring signal can be reduced (details will be described later). Of course, the electric circuit monitoring system 1 may be installed even when a leakage current breaker 81 is not installed in the electric circuit.

In addition, the electric circuit monitoring system 1 can detect the occurrence of an electric circuit leakage current based on the monitoring signal extracted by the signal extraction device 3. For example, when the resistance component of the AC current as the monitoring signal exceeds a threshold value, the electric circuit monitoring system 1 determines that an electric circuit leakage current has occurred.

Furthermore, functions similar to those of the electric circuit monitoring system 1 can be embodied in an electric circuit monitoring method. The electric circuit monitoring method of this embodiment has a signal input step and a signal extraction step. In the signal input step, a monitoring signal is input to an electric circuit for power distribution. In the signal extraction step, the monitoring signal is extracted from the electric circuit. In the signal input step, an AC signal having a higher frequency than the commercial frequency is intermittently input to the electric circuit as a monitoring signal.

The electrical circuit monitoring method can also be embodied in a program. The program of this embodiment is a program for causing one or more processors of a computer system to execute the electrical circuit monitoring method. The program may be recorded on a non-transitory recording medium that can be read by the computer system.

(detail)
(1) Overall Configuration Hereinafter, the electric circuit monitoring system 1 and a number of related configurations are collectively referred to as a power system 100. As shown in FIG. 1, the electric power system 100 includes a signal input device 2, a monitoring device 9, a power receiving facility 7, and a number of (two in FIG. 1) distribution boards 8. The power receiving facility 7 includes a transformer 71 and a number of (two in FIG. 1) feeders 72. Each of the multiple distribution boards 8 includes a signal extraction device 3, a main breaker 80, and a number of (two in FIG. 1) branch breakers 82. Each of the multiple branch breakers 82 is electrically connected to a load 201. The electric power system 100 also includes an electric circuit that electrically connects a commercial power source and the load 201. The transformer 71, the feeder 72, the main breaker 80, and the multiple branch breakers 82 each include a part of the electric circuit. The electric circuit also includes a first electric circuit 4, a second electric circuit 5, and a third electric circuit 6. The first electric circuit 4 , the second electric circuit 5 , and the third electric circuit 6 constitute the power system 100 .

The power system 100 also includes an electric circuit monitoring system 1. The electric circuit monitoring system 1 includes the above-mentioned signal input device 2, signal extraction device 3, and monitoring device 9.

(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 6600 V (effective value) transmitted from a commercial power source is applied to the primary winding 711 of the transformer 71. The transformer 71 transforms the AC voltage V0 of 6600 V applied to the primary winding 711 into, for example, an AC voltage of 200 V (effective value) applied to the secondary winding 712. Note that the AC voltage V0 received by the power receiving equipment 70 is a single-phase AC voltage in this embodiment, but may be a three-phase AC voltage.

The secondary winding 712 is electrically connected to the first electrical path 4. The first electrical path 4 is an electrical path between the secondary winding 712 and the multiple feeders 72. The first electrical path 4 includes a neutral conductor 40, a first voltage conductor 41, and a second voltage conductor 42. The first electrical path 4 further includes neutral conductors 40A and 40B branching off from the neutral conductor 40, first voltage conductors 41A and 41B branching off from the first voltage conductor 41, and second voltage conductors 42A and 42B branching off from the second voltage conductor 42.

The secondary winding 712 is provided with a center tap 713. The center tap 713 is electrically connected to the neutral conductor 40. The neutral conductor 40 is grounded via the ground conductor 44.

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.

A 100V AC voltage V11 (the potential of the first voltage line 41 with respect 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 with respect to the potential of the second voltage line 42) in phase with the AC voltage V11 is applied between the second voltage line 42 and the neutral line 40. Thus, an AC voltage of 200V is applied between the first voltage line 41 and the second voltage line 42.

The neutral conductor 40 branches into two neutral conductors 40A and 40B. The first voltage conductor 41 branches into two first voltage conductors 41A and 41B. The second voltage conductor 42 branches into two second voltage conductors 42A and 42B. The neutral conductor 40, the first voltage conductor 41, and the second voltage conductor 42 are electrically connected to one feeder 72 via the neutral conductor 40A, the first voltage conductor 41A, and the second voltage conductor 42A. The neutral conductor 40, the first voltage conductor 41, and the second voltage conductor 42 are electrically connected to another feeder 72 via the neutral conductor 40B, the first voltage conductor 41B, and the second voltage conductor 42B.

The number of electrical paths branched off from each of the neutral conductor 40, the first voltage conductor 41, and the second voltage conductor 42 is not limited to two, and may be three or more. In addition, the neutral conductor 40, the first voltage conductor 41, and the second voltage conductor 42 may be electrically connected to one feeder 72 without branching off.

Each of the multiple feeders 72 electrically connects the first electrical circuit 4 and the second electrical circuit 5 and protects the connection points.

A second electric 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 focused on. Below, the configuration of the secondary side of one of the multiple feeders 72 will be described.

The second electrical circuit 5 is an electrical circuit between the feeder 72 and the main breaker 80. The second electrical circuit 5 includes a neutral conductor 50, a first voltage conductor 51, and a second voltage conductor 52. The second electrical circuit 5 further includes neutral conductors 50A and 50B branching off from the neutral conductor 50, first voltage conductors 51A and 51B branching off from the first voltage conductor 51, and second voltage conductors 52A and 52B branching off from the second voltage conductor 52.

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

The neutral wire 50 branches into two neutral wires 50A and 50B. The first voltage wire 51 branches into two first voltage wires 51A and 51B. The second voltage wire 52 branches into two second voltage wires 52A and 52B. The neutral wire 50, the first voltage wire 51, and the second voltage wire 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 wire 51A, and the second voltage wire 52A. The neutral wire 50, the first voltage wire 51, and the second voltage wire 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 wire 51B, and the second voltage wire 52B.

(3) Distribution Board In this embodiment, the multiple distribution boards 8 each have the same configuration. The configuration of one distribution board 8 will be described below.

The distribution board 8 has a signal extraction device 3, a main breaker 80, and multiple (two in FIG. 1) branch breakers 82. The signal extraction device 3 will be described later.

The third electrical circuit 6 is an electrical circuit between the main breaker 80 and the multiple branch breakers 82. The third electrical circuit 6 includes a neutral conductor 60, a first voltage conductor 61, and a second voltage conductor 62. The third electrical circuit 6 further includes neutral conductors 60A and 60B branching off from the neutral conductor 60, a first voltage conductor 61A branching off from the first voltage conductor 61, and a second voltage conductor 62B branching off from the second voltage conductor 62.

The main breaker 80 has three primary terminals and three secondary terminals. The three primary terminals are electrically connected to a neutral conductor 50A, a first voltage conductor 51A, and a second voltage conductor 52A. The three secondary terminals are electrically connected to a neutral conductor 60, a first voltage conductor 61, and a second voltage conductor 62.

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

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 line 60, the first voltage line 61, and the second voltage line 62. For example, when focusing on branch breaker 82A among the multiple branch breakers 82, the two branch lines are the neutral line 60A and the first voltage line 61A. For example, when focusing on branch breaker 82B among the multiple branch breakers 82, the two branch lines are the neutral line 60B and the second voltage line 62B. The two branch lines may also be an electric wire branched from the first voltage line 61 and an electric wire branched from the second voltage line 62.

The two secondary terminals of each of the multiple branch breakers 82 are electrically connected to two electric wires 200 (insulated electric wires) for indoor wiring. A load 201 is electrically connected to these two electric wires 200 directly or via an outlet such as a socket. An AC power of 100V or 200V is supplied to the load 201. Representative loads 201 include lighting fixtures and air conditioning devices (air conditioners). For example, the two electric wires 200 may be electrically connected to the load 201 via an inverter 202.

The main breaker 80 in this embodiment is a leakage current breaker 81. When a leakage current is detected, the leakage current breaker 81 insulates (cuts off) the primary terminal from the secondary terminal.

(4) Electric Circuit Monitoring System The electric circuit monitoring system 1 is an electric leakage monitoring system of the Igr method. The Igr method is a method in which a signal is injected into an electric circuit and a resistance component of a leakage current is obtained based on the injected signal. The electric circuit monitoring system 1 includes a signal input device 2, a signal extraction device 3, and a monitoring device 9.

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 electric circuit via a transformer 20 arranged in the electric circuit. More specifically, the signal input device 2 inputs a monitoring signal to the grounding wire 44 of the power receiving equipment 7 by the transformer 20. The monitoring signal is an AC voltage signal with a higher frequency than the frequency (50 Hz or 60 Hz) 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 50 Hz and lower than 60 Hz, or higher than 60 Hz. The frequency of the monitoring signal is, for example, 1 kHz or less.

As shown in FIG. 2, the signal input device 2 has a transformer 20, an oscillator 21, a power supply unit 22, a control unit 23, and a first communication unit 24.

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. It is preferable that the power supply unit 22 has, for example, a step-down switching power supply circuit.

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

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 ground wire 44 (see FIG. 1) is passed through the central cavity of the ring-shaped magnetic core. When a sine wave AC voltage is applied from the oscillator 21 to the primary winding of the transformer 20, a sine wave induced voltage is induced in the ground wire 44 that passes through the ring-shaped magnetic core of the transformer 20. In other words, a monitoring signal consisting of a sine wave AC voltage is input (superimposed) to the sine wave AC voltages V11 and V12 applied between the neutral conductor 40 and the first voltage conductor 41, and between the neutral conductor 40 and the second voltage conductor 42. It is preferable that the transformer 20 be a split type transformer.

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 an 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, the first communication unit 24 preferably has a communication circuit that complies with serial communication standards such as RS-232C or RS-485. When a power line is used as the communication medium, the first communication unit 24 is preferably configured as a PLC (Power Line Communication) modem that performs power line carrier communication. When radio waves are used as the communication medium, the first communication unit 24 is preferably configured as a specific low power radio station, a wireless LAN communication device that uses radio waves in the 2.4 GHz or 5 GHz band, a short-distance wireless communication communication device that uses radio waves in the 2.4 GHz or 2.45 GHz band, or the like. Alternatively, the first communication unit 24 may be configured as a communication device that uses LPWA (Low Power Wide Area).

The control unit 23 preferably has 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.

As described above, the signal input device 2 inputs a monitoring signal to the electrical circuit (signal input step). More specifically, in the signal input step, multiple AC signals are periodically switched and input to the electrical circuit. Each of the multiple AC signals is a monitoring signal. The multiple AC signals have different frequencies. For example, as shown in FIG. 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 electrical circuit.

It is preferable that each of the AC signals S1 and S2 (monitoring signals) is a signal that corresponds to a portion of at least half a cycle and not more than one cycle of a sine wave signal. In the example shown in FIG. 4, each of the AC signals S1 and S2 (monitoring signals) is a signal that corresponds to a portion of one cycle of a sine wave signal. Also, there is an interval T0 between when the AC signal S1 (or S2) disappears (i.e., when the current becomes 0) and when the next AC signal S2 (or S1) is generated.

By increasing the interval T0 for inputting the monitoring signal to a certain extent, the possibility of the earth leakage breaker 81 installed in the electric circuit malfunctioning can be reduced. FIG. 5 shows an example of a current waveform (instantaneous value) detected by the earth leakage breaker 81 when an electric circuit connected to the earth leakage breaker 81 experiences an electric leakage. When an electric leakage occurs, the current rises temporarily, falls, and then rises again. For example, when 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, the earth leakage breaker 81 cuts off the electric circuit. Therefore, for example, when a lightning surge occurs in the electric circuit, even if the current exceeds the threshold Th1 once due to the surge current, the earth leakage breaker 81 does not cut off the electric circuit because it does not exceed the threshold Th1 thereafter. FIG. 6 shows an example of a current waveform (instantaneous value) detected by the earth leakage breaker 81 when a lightning surge occurs in an electric circuit connected to the earth leakage breaker 81.

If the monitoring signal is a continuous sinusoidal signal over several cycles, even if no leakage current occurs, the current on which the monitoring signal is superimposed may exceed the threshold value Th1, fall below the threshold value Th1, and then exceed the threshold value Th1 again within a specified time. This may cause the leakage current breaker 81 to cut off the electrical circuit. In contrast, by using an intermittent monitoring signal, the possibility that the leakage current breaker 81 will erroneously cut off the electrical circuit even when no leakage current occurs can be reduced. In other words, even if the current on which the monitoring signal is superimposed exceeds the threshold value Th1, it takes time for the current to next exceed the threshold value Th1, and therefore the condition for the leakage current breaker 81 to cut off the electrical circuit is no longer met. It is preferable that the interval T0 for inputting the monitoring signal is longer than the above-mentioned specified time.

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

The IEC standard also stipulates that earth leakage breakers should trip within 40 milliseconds. Therefore, in the signal input step, it is preferable to input a monitoring signal to the circuit intermittently at intervals of 40 milliseconds or more. In other words, it is preferable that T0 is 40 milliseconds or more.

In addition, in the signal input step, it is preferable to input a monitoring signal to the circuit intermittently at intervals of four times or less than 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, it is preferable that the interval T0 for inputting the monitoring signal is 12.5 x 4 = 50 milliseconds or less. In addition, in the signal input step, it is also preferable to input a monitoring signal to the circuit intermittently at intervals of five minutes or less. By inputting the monitoring signal at a relatively short interval, it is possible to increase the frequency with which the presence or absence of a ground leak can be determined.

An inverter 202 (see FIG. 1) may be connected to the electric circuit. A high-frequency signal generated by the inverter 202 may reach the earth leakage breaker 81, for example, via the ground. Therefore, in order to reduce the possibility of erroneously detecting the high-frequency signal generated by the inverter 202 as a leakage current, the earth leakage breaker 81 may be configured to, for example, filter (remove) the high-frequency components of the detection signal and detect an earth leakage based on the filtered detection signal.

The high-frequency signal generated by the inverter 202 is, for example, a signal with a carrier frequency, 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 from being mixed with the monitoring signal, it is preferable that the frequency of the monitoring signal is 1 kHz or less. It is also preferable that the frequency of the monitoring signal is smaller than the carrier frequency of the inverter 202 electrically connected to the electric circuit.

As described above, it is preferable that the AC signals S1 and S2 (monitoring signals) are each a signal equivalent to a portion of a sine-wave signal that is more than half a cycle and less than one cycle. Here, the term "the monitoring signal is a signal equivalent to a portion of a sine-wave signal that is more than half a cycle and less than one cycle" means that the waveform of the monitoring signal that is optionally injected has a shape of a portion of a sine-wave signal that is more than half a cycle and less than one cycle. For example, the term "the monitoring signal is a signal (half-wave signal) equivalent to a portion of a half cycle of a sine-wave signal" means that the waveform of the monitoring signal that is optionally injected is a half-wave waveform. Even if the waveform of the monitoring signal that is optionally injected is a half-wave waveform, a signal with a sign different from that of the monitoring signal may occur in the electric circuit following the optionally injected monitoring signal. For example, when the monitoring signal and the signal following the monitoring signal are measured, a waveform similar to that shown in FIG. 6 may be measured. That is, if the monitoring signal is a positive current, a negative current may occur after the current of the monitoring signal becomes 0. In such a case, the monitoring signal is also said to be a signal (half-wave signal) equivalent to a portion of a half cycle of a sine-wave signal.

Next, the signal extraction device 3 will be described. The signal extraction device 3 is arranged in each of the multiple distribution boards 8, for example, as shown in FIG. 1. The signal extraction device 3 extracts, for example, a monitoring signal from the second electric circuit 5. More specifically, the signal extraction device 3 extracts a monitoring signal input to the neutral conductor 50A, the first voltage conductor 51A, and the second voltage conductor 52A of the second electric circuit 5. In this way, the signal extraction device 3 monitors the insulation deterioration of the electric circuit relative to the ground.

The signal extraction device 3 has multiple sensors 30 (three in FIG. 1), a filter 31, a calculation unit 32, and a second communication unit 33.

The signal extraction device 3 extracts a monitoring signal from the electrical circuit via a sensor 30 arranged on the electrical circuit. In this embodiment, the sensor 30 is a current transformer. However, the sensor 30 may also be, for example, a magnetic resistance element or a Hall element.

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

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

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

The second case 302 is formed, for example, from a synthetic resin. The second case 302 is shaped like a rectangular parallelepiped. A second magnetic core 305 formed in a U-shape is housed inside the second case 302. A second recess 3020 having a semi-cylindrical surface is provided on the top surface of the second case 302. The second case 302 is attached to the first case 301 so as to be rotatable between a closed position (see FIG. 3A) in which the top surface of the second case 302 is in contact with the top surface of the first case 301, and an open position (see FIG. 3B) in which the top surface of the second case 302 is separated from the top surface of the first case 301. A protrusion 306 protrudes from the side surface of the first case 301. A U-shaped lock piece 307 protrudes from the side surface of the second case 302. The first case 301 and the second case 302 are fixed in the closed position by hooking the lock piece 307 on the protrusion 306 (see FIG. 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 ring-shaped magnetic core.

With the second case 302 rotated to the open position, an electrical circuit (neutral conductor 50A, first voltage conductor 51A, or second voltage conductor 52A) is inserted between the first recess 3010 of the first case 301 and the second recess 3020 of the second case 302. The second case 302 is then rotated from the open position to the closed position, and the lock piece 307 is hooked onto the protrusion 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.

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.

The current containing the frequency components of the monitoring signal extracted by the filter 31 is converted into a voltage signal having a voltage magnitude corresponding to the current value and input to the calculation unit 32.

The calculation unit 32 preferably has hardware including a microcontroller and software including a program executed by the microcontroller. The calculation unit 32 A/D converts 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 calculation unit 32 performs calculations based on the extracted data stored in the memory to detect leakage current (earth fault current) flowing from the electric circuit to the ground.

AC signals S1 and S2 are current signals, the frequency of AC signal S1 is f, and the frequency of AC signal S2 is xf (x>0, x≠1). The current values of AC signals S1 and S2 are _If and _Ixf , respectively. Here, _If and _Ixf are vectors having resistance and capacitance components. The resistance components of _If and _Ixf are I _R and I _R , respectively. Since the capacitance component is proportional to the frequency, the capacitance components of _If and _Ixf are _Ic and _xIC , respectively. Then, [Equation 1] and [Equation 2] are established.

[Equation 1]
^If2 = _{I R2} ^{+ I} _c2
[Equation 2]
_Ixf2 ^{= I} _R2 + (xI _c ) ²
Therefore, the following equation 3 holds true:

[Equation 3]
_Ixf2 ^- _If2 ⁼ ( ^{x2 -} 1) _Ic2
Therefore, [Equation 4] and [Equation 5] hold true.

[Equation 4]
_Ic2 ⁼ ( _Ixf2 ^- _If2 ⁾ / ( ^x2 - 1)
[Equation 5]
_IR2 = ^{( x2} _{If2 - Ixf2} ^{) /} ( ^x2 - 1)

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

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

The higher the frequency of the monitoring signal, the greater the effect of the capacitive component of the leakage current. Therefore, the electrical circuit monitoring system 1 makes it possible to determine the occurrence of a leakage current based on the resistive component by separating the capacitive component from the resistive component through calculation. This improves the accuracy of the determination.

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 determining whether or not there is a leakage current.

The monitoring device 9 is, for example, an alarm device or a display device that allows a user to monitor the occurrence of an electric leakage. As shown in FIG. 1, the monitoring device 9 has a third communication unit 91, a memory unit 92, and a notification unit 93.

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

The memory unit 92 is a storage device configured with a hard disk drive (HDD) or a solid state drive (SSD) or the like. The memory unit 92 stores the information acquired by the third communication unit 91 from the signal extraction device 3.

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

The notification unit 93 may, for example, notify whether or not there is a leakage current, or the magnitude of the leakage current.

In addition, when the calculation unit 32 detects the occurrence of an electric leakage current, the electric circuit monitoring system 1 may open a switch installed on the electric circuit to interrupt the electric circuit. In other words, the electric circuit monitoring system 1 may be used as an electric leakage circuit breaker.

(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 conductor 50A, the first voltage conductor 51A, and the second voltage conductor 52A. Furthermore, the signal extraction device 3 may have two or more sets of sensors 30 for extracting monitoring signals, with three sensors 30 being one set. Furthermore, a plurality of signal extraction devices 3 may be provided. Furthermore, the number of sensors 30 may be one or more.

The sensor 30 can be placed at various locations in the electrical circuit where leakage current is to be detected. In FIG. 1, each of the locations indicated by a dashed circle P is an example of a location where the sensor 30 can be placed. That is, the sensor 30 may be placed in, for example, one, two, or all of the first electrical circuit 4, the second electrical circuit 5, and the third electrical circuit 6.

Specifically, the sensor 30 may be arranged, for example, in the neutral conductor 40A, the first voltage conductor 41A, and the second voltage conductor 42A. The sensor 30 may also be arranged, for example, in the neutral conductor 40B, the first voltage conductor 41B, and the second voltage conductor 42B.

The sensor 30 may also be arranged, for example, in the neutral conductor 60A and the first voltage conductor 61A. The sensor 30 may also be arranged, for example, in the neutral conductor 60B and the second voltage conductor 62B.

The sensor 30 may also be disposed, for example, on the electric wire 200.

It is not essential that the signal extraction device 3 is a component of the distribution board 8. When the sensor 30 is disposed in the first electrical circuit 4, the signal extraction device 3 may be a component of the power receiving equipment 7. In addition, the signal extraction device 3 may be a component independent of both the distribution board 8 and the power receiving equipment 7.

The sensor 30 may also be built into, for example, the main breaker 80 or the branch breaker 82.

When sensors 30 are placed in multiple locations, when a leakage current occurs, the electrical circuit monitoring system 1 can identify the location of the leakage current by determining which sensor 30 has detected the leakage current.

(6) Advantages In the electric circuit monitoring system 1 of this embodiment, the signal input device 2 intermittently inputs a signal having a higher frequency than the commercial frequency as a monitoring signal to the electric circuit. Therefore, the signal input device 2 that generates the monitoring signal can be made smaller than when the monitoring signal is a DC signal or an AC signal having a lower frequency than the commercial frequency. More specifically, the transformer 20 of the configuration of the signal input device 2 can be made smaller. The transformer 20 has a ring-shaped magnetic core, and inputs the monitoring signal to the electric circuit by inducing an induced voltage in the ground wire 44 that penetrates the ring-shaped magnetic core. If the voltage of the monitoring signal is V, the magnetic flux penetrating 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 greater the change in the magnetic flux φ per unit time, so even if the area S is relatively small, a voltage V that can be detected by the signal extraction device 3 can be obtained. By making the transformer 20 smaller, the manufacturing cost of the transformer 20 can be reduced.

In addition, because the transformer 20 is small, it is easy to make the transformer 20 a split-type transformer. Making the transformer 20 a split-type transformer simplifies the installation work of the transformer 20, for example, in that it is possible to install the transformer 20 without stopping the supply of power in the electric circuit.

Furthermore, since the monitoring signal is input intermittently, as described above, even if a leakage current breaker 81 is installed in the electrical circuit, the possibility that the leakage current breaker 81 will erroneously detect the occurrence of a leakage current based on the monitoring signal can be reduced.

(Modification of the embodiment)
Modifications of the embodiment will be listed below. The following modifications may be implemented in appropriate combination.

In the embodiment, the case where the electric circuit monitoring system 1 is installed in a high-voltage power receiving facility has been described. In contrast, the electric circuit monitoring system 1 may also be installed in a low-voltage power receiving facility.

In the embodiment, the case where the electric circuit monitoring system 1 is introduced into a single-phase three-wire electric circuit has been described. However, the electric circuit monitoring system 1 may be introduced into electric circuits of other power distribution methods, for example, single-phase two-wire, three-phase three-wire, or three-phase four-wire electric circuits.

The location where the transformer 20 of the signal input device 2 is placed is not limited to the first electrical path 4. The transformer 20 may be placed, for example, in the second electrical path 5 or the third electrical path 6.

It is not essential that the first electric circuit 4, the second electric circuit 5, and the third electric circuit 6 are branched into multiple parts.

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

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

The signal input device 2 may transmit a communication signal 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. The notification of these timings is performed by a command 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 notified by the received communication signal. Specifically, the signal extraction device 3 may extract the monitoring signal from the start of inputting the monitoring signal to the end of inputting the monitoring signal, i.e., during the period during which the monitoring signal is being input, and determine the presence or absence of a leakage current based on the extracted monitoring signal. This can further reduce the possibility that the signal extraction device 3 will erroneously detect the occurrence of a leakage current.

The executing entity of the electric circuit monitoring system 1 or the electric circuit monitoring method in the present disclosure includes a computer system. The computer system is mainly composed of a processor and a memory as hardware. At least a part of the function of the executing entity of the electric circuit monitoring system 1 or the electric circuit monitoring method in the present 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, may be provided through an electric communication line, or may be recorded and provided in a non-transitory recording medium such as a memory card, an optical disk, or a hard disk drive that can be read by the computer system. The processor of the computer system is composed of one or more electronic circuits including a semiconductor integrated circuit (IC) or a large scale integrated circuit (LSI). The integrated circuits such as IC or LSI referred to here are called different names depending on the degree of integration, and include integrated circuits called system LSI, VLSI (Very Large Scale Integration), or ULSI (Ultra Large Scale Integration). Furthermore, a field-programmable gate array (FPGA) that is programmed after the LSI is manufactured, or a logic device that allows reconfiguration of the connection relationship within the LSI or reconfiguration of the circuit partition within the LSI, can also be used as a processor. The electronic circuits may be integrated into one chip, or may be distributed among multiple chips. The chips may be integrated into one device, or may be distributed among multiple devices. The computer system referred to here includes a microcontroller having one or more processors and one or more memories. Therefore, the microcontroller is also composed of one or more electronic circuits including a semiconductor integrated circuit or a large-scale integrated circuit.

In addition, in the embodiment, multiple functions that are integrated in one device may be distributed among multiple devices. For example, the device that constitutes the filter 31 of the signal extraction device 3 may be provided separately from the device that constitutes the calculation unit 32.

Conversely, in an embodiment, at least some of the functions of the electrical circuit monitoring system 1 that are distributed among multiple devices may be consolidated into one device. For example, at least some of the signal input device 2 and at least some of the signal extraction device 3 may be consolidated into one device.

(summary)
The above-described embodiments and the like disclose the following aspects.

The electric circuit monitoring method according to the first aspect includes a signal input step and a signal extraction step. In the signal input step, a monitoring signal is input to an electric circuit for power distribution. In the signal extraction step, the monitoring signal is extracted from the electric circuit. In the signal input step, an AC signal having a higher frequency than the commercial frequency is intermittently input to the electric circuit as the monitoring signal.

According to the above configuration, when a leakage current breaker (81) is installed in an electric circuit, the possibility that the leakage current breaker (81) will erroneously detect the occurrence of a leakage current based on a monitoring signal can be reduced.

In addition, the electric circuit monitoring method according to the second aspect is the first aspect, 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 electric circuit. The plurality of AC signals (S1, S2) have different frequencies.

With the above configuration, it is 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.

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

The above configuration allows the occurrence of a leakage current to be determined based on the resistance component by separating the capacitance component from the resistance component through calculation. This improves the accuracy of the determination.

In addition, in the electric circuit monitoring method according to the fourth aspect, in any one of the first to third aspects, the monitoring signal is a signal that corresponds to a portion of a sine wave signal that is at least half a cycle and not more than one cycle.

The above configuration reduces the possibility of false detection by the earth leakage breaker (81).

The fifth aspect of the electrical circuit monitoring method is any one of the first to fourth aspects, in which in the signal input step, a monitoring signal is intermittently input to the electrical circuit at intervals longer than the generation time of the monitoring signal.

The above configuration reduces the possibility of false detection by the earth leakage breaker (81).

The sixth aspect of the electrical circuit monitoring method is any one of the first to fifth aspects, in which the signal input step intermittently inputs a monitoring signal to the electrical circuit at intervals of 40 milliseconds or more.

The above configuration reduces the possibility of false detection by the earth leakage breaker (81).

The seventh aspect of the electrical circuit monitoring method is any one of the first to sixth aspects, in which in the signal input step, a monitoring signal is intermittently input to the electrical circuit at intervals of four times or less than the generation time of the monitoring signal.

The above configuration allows the frequency of checking for the presence or absence of a leakage current to be increased.

In addition, in the electrical circuit monitoring method according to the eighth aspect, in any one of the first to seventh aspects, the frequency of the monitoring signal is 1 kHz or less.

The above configuration reduces the possibility of the high-frequency signal generated by the inverter (202) being mixed with the monitoring signal.

In addition, in the electric circuit monitoring method according to the ninth aspect, in any one of the first to eighth aspects, the frequency of the monitoring signal is lower than the carrier frequency of the inverter (202) electrically connected to the electric circuit.

The above configuration reduces the possibility of the high-frequency signal generated by the inverter (202) being mixed with the monitoring signal.

Configurations other than the first aspect are not essential to the electrical circuit monitoring system (1) and may be omitted as appropriate.

The program according to the tenth aspect is a program for causing one or more processors of a computer system to execute the circuit monitoring method according to any one of the first to ninth aspects.

According to the above configuration, when a leakage current breaker (81) is installed in an electric circuit, the possibility that the leakage current breaker (81) will erroneously detect the occurrence of a leakage current based on a monitoring signal can be reduced.

The electric circuit monitoring system (1) according to the eleventh aspect includes a signal input device (2) and a signal extraction device (3). The signal input device (2) inputs a monitoring signal to an electric circuit for power distribution. The signal extraction device (3) extracts the monitoring signal from the electric circuit. The signal input device (2) intermittently inputs a signal having a higher frequency than the commercial frequency as a monitoring signal to the electric circuit.

According to the above configuration, when a leakage current breaker (81) is installed in an electric circuit, the possibility that the leakage current breaker (81) will erroneously detect the occurrence of a leakage current based on a monitoring signal can be reduced.

In addition, in the electrical circuit monitoring system (1) according to the twelfth aspect, in the eleventh aspect, the signal input device (2) transmits a communication signal notifying the timing of inputting the monitoring signal to the signal extraction device (3). The signal extraction device (3) extracts the monitoring signal in synchronization with the timing notified by the received communication signal.

The above configuration can further reduce the possibility of false detection of an electrical leakage.

Not limited to the above aspects, various configurations (including modified examples) of the electrical circuit monitoring system (1) according to the embodiment can be embodied in an electrical circuit monitoring method, a (computer) program, or a non-transitory recording medium on which a program is recorded.

1 Electrical circuit monitoring system 2 Signal input device 3 Signal extraction device 202 Inverters S1, S2 AC signal

Claims (12)

A signal input step of inputting a monitoring signal into an electric line for power distribution;
A signal extraction step of extracting the monitoring signal from the electrical line,
In the signal input step, an AC signal having a higher frequency than a commercial frequency is intermittently input to the electric circuit as the monitoring signal.
Methods for monitoring electrical circuits. In the signal input step, a plurality of AC signals, each of which is the monitoring signal, are periodically switched and input to the electrical circuit;
The plurality of AC signals have different frequencies.
The method for monitoring an electrical circuit according to claim 1 . The method further includes a calculation step of calculating a current corresponding to a resistance component of a leakage current flowing between the electric circuit and the ground based on the plurality of AC signals.
The method for monitoring an electrical circuit according to claim 2. The monitoring signal is a signal corresponding to a portion of a sine wave signal that is equal to or greater than half a period and equal to or less than one period.
The method for monitoring an electrical circuit according to claim 1 . In the signal input step, the supervisory signal is intermittently input to the electrical circuit at intervals longer than a generation time of the supervisory signal.
The method for monitoring an electrical circuit according to claim 1 . In the signal input step, the monitoring signal is input to the electrical circuit intermittently at intervals of 40 milliseconds or more.
The method for monitoring an electrical circuit according to claim 1 . In the signal input step, the monitoring signal is intermittently input to the electric circuit at intervals of four times or less than a generation time of the monitoring signal.
The method for monitoring an electrical circuit according to claim 1 . The frequency of the monitoring signal is 1 kHz or less.
The method for monitoring an electrical circuit according to claim 1 . The frequency of the monitoring signal is lower than a carrier frequency of an inverter electrically connected to the electric path.
The method for monitoring an electrical circuit according to claim 1 . 2. A method for causing one or more processors of a computer system to execute the electrical line monitoring method according to claim 1,
program. a signal input device for inputting a monitoring signal into a distribution line;
a signal extracting device that extracts the monitoring signal from the electrical line,
The signal input device intermittently inputs a signal having a higher frequency than a commercial frequency as the monitoring signal to the electric circuit.
Electrical circuit monitoring system. the signal input device transmits a communication signal to the signal extraction device to notify the timing of inputting the monitoring signal;
the signal extraction device extracts the supervisory signal in synchronization with the timing notified by the received communication signal;
The electrical circuit monitoring system according to claim 11.

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