Ground-fault circuit interrupter

Abstract

To provide a ground-fault circuit interrupter in which an accuracy of a ground-fault examination is increased.SOLUTION: A ground-fault circuit interrupter comprises: a zero-phase-sequence current transformer having a power supply wire connected between a power supply and a load, a magnetic core, and a detection coil that is wound to the magnetic core and detects a leakage current from the power supply wire; an A / D conversion circuit that is connected to the detection coil, and converts a signal of the leakage current detected by the detection coil into a first digital signal; a control circuit that controls a ground-fault on the basis of the first digital signal; a pulse current output element that outputs a pulse current in a period that is different from the leakage current; and an examination coil that is wound at a position that is different from the detection coil in the magnetic core, and flows the pulse current obtained by a pulse current output element. The detection coil detects an examination current excited by the pulse current flowing in the examination coil. The A / D conversion circuit converts a signal of the examination current detected by the detection coil into a second digital signal. The control circuit controls an examination fault on the basis of the second digital signal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an earth leakage circuit breaker. [Background technology]

[0002] There is known an earth leakage circuit breaker that detects an earth leakage from a power supply line connected between a power source and a load and cuts off the power supply from the power source to the load. Also, an earth leakage circuit breaker that can perform an earth leakage interruption test has been disclosed (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5866993 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for improving the accuracy of earth leakage current interruption tests for earth leakage current interrupters.

[0005] The present disclosure aims to provide an earth leakage circuit breaker that improves the accuracy of an earth leakage interruption test. [Means for solving the problem]

[0006] In a first aspect, the zero-phase current transformer includes a power supply line connected between a power supply and a load, a magnetic core, and a detection coil wound around the magnetic core to detect a leakage current from the power supply line, an A / D conversion circuit connected to the detection coil to convert a signal of the leakage current detected by the detection coil into a first digital signal, a control circuit controlling a leakage current interruption based on the first digital signal, a pulse current output element outputting a pulse current with a period different from that of the leakage current, and a test coil wound around the magnetic core at a position different from that of the detection coil to pass the pulse current obtained from the pulse current output element, wherein the detection coil detects a test current induced by the pulse current flowing in the test coil, the A / D conversion circuit converts the signal of the test current detected by the detection coil into a second digital signal, and the control circuit controls a test interruption based on the second digital signal. Effect of the Invention

[0007] According to the technique of the present disclosure, the accuracy of an earth leakage interruption test can be improved. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing an example of an overall configuration of an earth leakage circuit breaker according to an embodiment; [Diagram 2] 4 is a diagram showing an example of a pulse current flowing through a test coil of the earth leakage circuit breaker according to the embodiment. FIG. [Diagram 3] 1 is a diagram showing an example of a test current flowing through a detection coil of a zero-phase current transformer in an earth leakage circuit breaker according to an embodiment. FIG. [Figure 4] 4 is a diagram showing an example of a test signal processed by a control circuit of the earth leakage circuit breaker according to the embodiment; FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an earth leakage circuit breaker according to an embodiment will be described with reference to the drawings. Note that "connection" is not limited to physical connection, but may include electrical connection. For example, connecting an object A to an object B is not limited to the case where the object A is conductively connected to the object B (e.g., at the same potential), but may include the case where the object A is conductively connected to the object B via the object C.

[0010] The earth leakage circuit breaker 10 according to the embodiment is an electronic earth leakage circuit breaker that converts an analog signal relating to a leakage current into a digital signal and detects the presence or absence of an earth leakage based on the converted digital signal.

[0011] The earth leakage circuit breaker 10 is connected between the power source 1 and the load 3. The earth leakage circuit breaker 10 has an earth leakage circuit breaker function that operates to cut off the power supply from the power source 1 to the load 3 in response to detection of an electric leakage. The earth leakage circuit breaker 10 also has a test function that tests whether the earth leakage circuit breaker function works properly. The earth leakage circuit breaker 10 is intended to improve the accuracy of testing the earth leakage circuit breaker function.

[0012] <Earth leakage breaker function> As a premise for explaining the test function of the earth leakage circuit breaker 10, first, the earth leakage circuit breaker function of the earth leakage circuit breaker 10 will be explained. The configuration related to the earth leakage circuit breaker function of the earth leakage circuit breaker 10 will be explained with reference to Fig. 1. Fig. 1 is a schematic diagram showing the overall configuration of the earth leakage circuit breaker 10 of the present embodiment.

[0013] 1, the earth leakage circuit breaker 10 includes power feeders 20a and 20b, a zero-phase current transformer 30, an amplifier circuit 41, an A / D conversion circuit 42, a control circuit 50, a non-volatile memory 52, a sensitivity current changeover switch 55, a tripping unit 60, and a power supply circuit 71. The earth leakage circuit breaker 10 further includes a test start switch 110, a pulse current output element 120, a current limiting element 130, and a test coil 140, which are components for performing a test function. These components for performing the test function will be described separately.

[0014] Each of the power feeders 20a and 20b is connected between the power source 1 and the load 3. Power transmitted from the power source 1 is supplied to the load 3 through the power feeders 20a and 20b. In other words, each of the power feeders 20a and 20b corresponds to an electric path for supplying power from the power source 1 to the load 3.

[0015] Here, an example of the power source 1 is a power system that transmits AC power. The power source 1 may be a commercial power system or another power system. The power source 1 may transmit three-phase AC power having U, V, and W phases, or may transmit single-phase AC power.

[0016] The load 3 is a device that is driven by power transmitted through the power source 1 and the power supply lines 20a and 20b. An example of the load 3 is an electric motor such as a motor. However, the type of the load 3 is not limited to this.

[0017] One end of the power feeder 20a is connected to the power source 1 through a power source side terminal 22a of the earth leakage circuit breaker 10. The other end of the power feeder 20a is connected to the load 3 through a load side terminal 23a of the earth leakage circuit breaker 10. In addition, one end of the power feeder 20b is connected to the power source 1 through a power source side terminal 22b of the earth leakage circuit breaker 10. The other end of the power feeder 20b is connected to the load 3 through a load side terminal 23b of the earth leakage circuit breaker 10.

[0018] The power feeder 20a further includes a cutoff switch for switching the power feeder 20a between open and closed states. The power feeder 20b further includes another cutoff switch for switching the power feeder 20b between open and closed states. When the contacts of each cutoff switch are closed, power is supplied from the power source 1 to the load 3 through an electric path including the power feeders 20a and 20b. In response to the cutoff operation of the tripping unit 60, the contacts of each cutoff switch are opened. In this case, the power feeders 20a and 20b are cut off. Note that illustration of each cutoff switch is omitted.

[0019] When three-phase AC power having U, V, and W phases is transmitted from the power source 1, the earth leakage circuit breaker 10 further includes another power feeder. The further power feeder is connected between the power source 1 and the load 3, similar to the power feeders 20a and 20b, and includes a cutoff switch that opens the contacts in response to the cutoff operation of the tripping unit 60.

[0020] When AC power is transmitted from the power source 1 to the load 3 through three power feeders including the power feeders 20a and 20b, for example, the power feeder 20a transmits U-phase AC power, the power feeder 20b transmits V-phase AC power, and a power feeder other than the power feeders 20a and 20b transmits W-phase AC power.

[0021] In the following, an example will be described in which two power feeders 20a and 20b are used as the power feeders connected between the power source 1 and the load 3. However, the same description also applies to the case in which the earth leakage circuit breaker 10 has three power feeders including the power feeders 20a and 20b and another power feeder.

[0022] The zero-phase-sequence current transformer 30 detects leakage current occurring in the power supply lines 20a and 20b. As shown in Fig. 1, the zero-phase-sequence current transformer 30 includes a ring-shaped magnetic core 31 and a detection coil 32. The detection coil 32 is a winding wound around the magnetic core 31.

[0023] The magnetic core 31 is disposed around the outside of the power feeders 20a and 20b. That is, the power feeders 20a and 20b pass through the inside of the magnetic core 31. The material constituting the magnetic core 31 is not particularly limited as long as it is a material that passes a magnetic flux therethrough in response to a current flowing through the power feeders 20a and 20b. An example is an Fe-Ni based magnetic alloy.

[0024] The detection coil 32 is a coil also called a secondary winding in the zero-phase current transformer 30. The detection coil 32 detects a current excited by a change in the magnetic flux density in the magnetic core 31. In other words, the detection coil 32 corresponds to a detection unit for detecting a leakage current in the zero-phase current transformer 30.

[0025] Here, when a leakage current occurs in the power feeders 20a and 20b, the composite value (magnitude of the composite vector) of the phase currents flowing through the power feeders 20a and 20b becomes a value other than "0." As a result, the magnetic flux density in the magnetic core 31 changes, and an excitation current is induced in the detection coil 32. As a result, the detection coil 32 detects the leakage current.

[0026] On the other hand, when no leakage current occurs in the power feeders 20a and 20b, the composite value (magnitude of the composite vector) of the phase currents flowing through the power feeders 20a and 20b is 0. As a result, the magnetic flux density in the magnetic core 31 does not change, and no excitation current flows through the detection coil 32. In other words, the detection coil 32 does not detect the leakage current.

[0027] The amplifier circuit 41 is connected to both ends of the detection coil 32. The amplifier circuit 41 amplifies a signal of a leakage current detected by the detection coil 32. An output terminal of the amplifier circuit 41 is connected to an input terminal of an A / D conversion circuit 42. The amplifier circuit 41 outputs the amplified current signal to the A / D conversion circuit 42.

[0028] The A / D conversion circuit 42 converts the signal output from the amplifier circuit 41 into a digital signal. Specifically, the A / D conversion circuit 42 performs processing of sampling, quantization, and encoding of the signal output from the amplifier circuit 41, and converts the current signal into a digital signal. The digital signal based on the leakage current signal detected by the detection coil 32 corresponds to the "first digital signal."

[0029] The period of sampling performed by the A / D conversion circuit 42 is shorter than the period of the leakage current. The period of the leakage current roughly corresponds to the period of the AC power (AC current) transmitted from the power source 1. In other words, the period of sampling performed by the A / D conversion circuit 42 is shorter than the period of the AC power (AC current) transmitted from the power source 1.

[0030] For example, when an AC current having a frequency of 50 Hz is transmitted from the power source 1, the period of the leakage current is about 0.01 seconds. In order to improve the detection accuracy of the leakage current, the sampling period is preferably about 0.3 ms (1 / 30 of the period of the leakage current) to about 2 ms (1 / 20 of the period of the leakage current). However, the period of the sampling performed by the A / D conversion circuit 42 is not limited to this.

[0031] An output terminal of the A / D conversion circuit 42 is connected to an input terminal of the control circuit 50. The A / D conversion circuit 42 outputs a sequence of converted digital signals to the control circuit 50. Note that, although the illustrated A / D conversion circuit 42 is a circuit separate from the control circuit 50, it may be a circuit integrated with the control circuit 50.

[0032] The control circuit 50 executes leakage detection processing to detect leakage in the power feeders 20a and 20b, and controls the interruption of the power feeders 20a and 20b. Specifically, the control circuit 50 processes the digital signal output from the A / D conversion circuit 42, and detects leakage in the power feeders 20a and 20b. The interruption based on the leakage detection is an example of "leakage interruption."

[0033] The control circuit 50 is, for example, a microcomputer including a CPU (Central Processing Unit) and a ROM (Read Only Memory) that stores programs executed by the CPU, etc. Also, a part or all of the arithmetic processing functions of the CPU included in the control circuit 50 may be assigned to other electronic circuits such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

[0034] An example of the leakage current detection process executed by the control circuit 50 is as follows. First, the control circuit 50 calculates, for example, the effective value of the leakage current based on the digital signal output from the A / D conversion circuit 42. The control circuit 50 also compares the calculated effective value of the leakage current with a threshold value. If the effective value of the leakage current is equal to or greater than the threshold value, the control circuit 50 detects the leakage current and outputs a tripping signal for operating the tripping unit 60. On the other hand, if the effective value of the leakage current is less than the threshold value, the control circuit 50 does not output a tripping signal. In this case, the tripping unit 60 does not operate, and the power feeders 20a, 20b are not tripped.

[0035] The control circuit 50 may calculate other electrical information related to the leakage current, such as the maximum value or average value of the leakage current, from the sequence of digital signals output from the A / D conversion circuit 42. Furthermore, the control circuit 50 may detect a leakage current based on the other calculated electrical information.

[0036] It is preferable that the control circuit 50 generates leakage current interruption information in response to detection of leakage current. It is also preferable that the control circuit 50 outputs the generated leakage current interruption information to the non-volatile memory 52. ​​Here, it is preferable that the leakage current interruption information includes, for example, information such as the effective value of leakage current and various other information related to leakage current, as well as interruption cause information for identifying that the interruption is due to an actual leakage current.

[0037] The non-volatile memory 52 is a storage medium connected to the control circuit 50. The non-volatile memory 52 also stores leakage current interruption information and the like output from the control circuit 50. Examples of non-volatile memories include storage media such as flash memory and EEPROM (Electrically Erasable Programmable Read-Only Memory). However, non-volatile memories are not limited to these.

[0038] The illustrated non-volatile memory 52 is a storage medium separate from the control circuit 50, but may be a storage medium integrated with the control circuit 50. The non-volatile memory 52 is an example of a "storage unit".

[0039] The sensitivity current changeover switch 55 is a switch that changes the threshold value that the control circuit 50 refers to when performing leakage detection processing. The sensitivity current changeover switch 55 changes between a plurality of sensitivity currents corresponding to settable threshold values, for example, in response to an operation by an operator. The sensitivity current changeover switch 55 may be capable of discretely switching the sensitivity current, for example, to 100 mA, 1 A, 10 A, etc. Alternatively, the sensitivity current changeover switch 55 may be capable of continuously switching the sensitivity current within a current range of, for example, 100 mA to 10 A.

[0040] The tripping unit 60 is an electromagnetic tripping device including a tripping coil 61 and a switch 62 that excites the tripping coil 61. However, the tripping unit 60 may be a tripping device or a switching circuit that operates in another manner.

[0041] The tripping coil 61 is disposed near the breaker switches provided on the power supply lines 20a and 20b. One end of the tripping coil 61 is connected to a power supply circuit 71. The other end of the tripping coil 61 is connected to a switch 62.

[0042] The switch 62 is a switching element that excites the tripping coil 61 in response to a tripping signal from the control circuit 50. For example, the switch 62 is a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) including a control electrode 62a (e.g., a gate electrode) connected to the control circuit 50, a first main electrode 62b (e.g., a source electrode) connected to the tripping coil 61, and a second main electrode 62c (e.g., a drain electrode) that functions as a ground terminal.

[0043] In response to the tripping signal output from the control circuit 50, the switch 62 is turned on. This causes a current to flow through the tripping coil 61, exciting the tripping coil 61. As a result, the contacts of the tripping switch open, and each of the power feeders 20a and 20b is interrupted.

[0044] The power supply circuit 71 includes an input terminal connected to the power supply line 20a, another input terminal connected to the power supply line 20b, and output terminals connected to the control circuit 50 and the tripping unit 60. The power supply circuit 71 preferably includes another output terminal connected to the current limiting element 130.

[0045] The power supply circuit 71 converts the AC power transmitted from the power supply lines 20a, 20b into DC power, and reduces the voltage value of the converted DC power to a voltage value at which the control circuit 50 can operate.

[0046] Examples of the power supply circuit 71 include a regulator circuit or a converter circuit including a plurality of switching elements configured from semiconductor elements such as IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs, etc. However, the power supply circuit 71 is not limited to a regulator circuit, a converter circuit, etc.

[0047] <Test function> Next, the test function of the earth leakage circuit breaker 10 will be described with reference to Figs. 1 to 4. Fig. 1 is a schematic diagram showing the overall configuration of the earth leakage circuit breaker 10 of this embodiment. Fig. 2 is a diagram showing an example of a pulse current flowing through the test coil 140. Fig. 3 is a diagram showing an example of a test current flowing through the detection coil 32 of the zero-phase current transformer 30. Fig. 4 is a diagram showing an example of a test signal processed by the control circuit 50.

[0048] The earth leakage circuit breaker 10 includes components for performing an earth leakage circuit breaking function, such as power supply lines 20a, 20b, a zero-phase-sequence current transformer 30, an amplifier circuit 41, an A / D conversion circuit 42, a control circuit 50, a non-volatile memory 52, a sensitivity current changeover switch 55, and a tripping unit 60, as well as components for performing a test function, such as a test start switch 110, a pulse current output element 120, a current limiting element 130, and a test coil 140.

[0049] Each component for performing the earth leakage breaker function in the earth leakage breaker 10 also operates appropriately in order for the earth leakage breaker 10 to perform the test function. Here, during the test, the control circuit 50 executes a simulation process for simulating an earth leakage detection process based on a test signal, which is a digital signal.

[0050] The test start switch 110 is connected to the control circuit 50. The test start switch 110 has a contact that closes in response to, for example, an operation by an operator. When the contact is closed, the test start switch 110 outputs a test start signal to the control circuit 50. In response to the input of the test start signal from the test start switch 110, the control circuit 50 outputs a drive signal to the pulse current output element 120.

[0051] The control circuit 50 operates at a relatively low voltage (for example, 5V). The test start switch 110 is a member that an operator directly touches. Therefore, by connecting the test start switch 110 to the control circuit 50 that operates at a low voltage, it is possible to more reliably prevent the operator from receiving an electric shock or the like.

[0052] The pulse current output element 120 sequentially outputs a plurality of pulse currents to the test coil 140 in response to a drive signal output from the control circuit 50. As shown in FIG. 1, the pulse current output element 120 of this embodiment is a switching element including a MOSFET. However, the pulse current output element 120 may be a switching element including other semiconductor elements such as an IGBT or a bipolar transistor. The pulse current output element 120 may also be a relay including a relay element.

[0053] The pulse current output element 120 includes, for example, a control electrode 121 corresponding to a gate electrode, a first main electrode 122 corresponding to a source electrode, and a second main electrode 123 corresponding to a drain electrode. The control electrode 121 is connected to a control circuit 50. The first main electrode 122 is connected to a power supply circuit 71 through a current limiting element 130. The second main electrode 123 is connected to a test coil 140. When a drive signal from the control circuit 50 is input to the control electrode 121, the first main electrode 122 and the second main electrode 123 are brought into conduction. As a result, a pulse current corresponding to the ON / OFF of the drive signal from the control circuit 50 is output sequentially to the test coil 140.

[0054] It is preferable that the driving power of the pulse current output element 120 is supplied from each of the power feeders 20a and 20b through the power supply circuit 71. In this way, the AC voltage value transmitted from the power feeders 20a and 20b can be adjusted through the power supply circuit 71 to a DC voltage value at which the pulse current output element 120 is appropriately driven.

[0055] The current supplied to the pulse current output element 120 is preferably limited to a desired value by the current limiting element 130. An example of the current limiting element 130 is a resistive element. The current limiting element 130 may also be another element having a current limiting function. This makes it possible to adjust the magnitude of the peak value of each pulse current output from the pulse current output element 120. As a result, a test can be performed using a pulse current having a peak value corresponding to the sensitivity current of the sensitivity current changeover switch 55, and it can be confirmed whether or not a leakage current is appropriately detected for each threshold value corresponding to each of the multiple sensitivity currents.

[0056] Each pulse current output from the pulse current output element 120 is a square-wave current that flows for a period corresponding to the pulse width. Here, "square-wave" includes, for example, a square wave having angular transient distortion that appears at the initial timing when the current flows. The period of the pulse current output from the pulse current output element 120 is shorter than the period of the leakage current. The period of the pulse current corresponds, for example, to the time between the starting point of an arbitrary pulse current (for example, the pulse current S11 shown in FIG. 2) and the starting point of the next pulse current (for example, the pulse current S12) (time T1 shown in FIG. 2).

[0057] As will be described later, the test signal derived from the pulse current is transmitted to the control circuit 50 through the detection coil 32, the amplifier circuit 41, and the A / D conversion circuit 42 of the zero-phase current transformer 30. The test signal transmitted to the control circuit 50 is used for simulation processing of the control circuit 50. Incidentally, the power supply lines 20a and 20b are energized even during the test period. Therefore, if a leakage current occurs during the test, the signal derived from the leakage current may be mixed as noise into the transmission path of the test signal. Therefore, by making the period of the pulse current different from that of the leakage current, the control circuit 50 can distinguish the test signal derived from the pulse current from the signal derived from the leakage current. Furthermore, by setting the period of the pulse current shorter than that of the leakage current, the control circuit 50 can more accurately distinguish the test signal derived from the pulse current from the signal derived from the leakage current. Therefore, the accuracy of the earth leakage interruption test can be improved.

[0058] The period of the pulse current is preferably related to the period of sampling executed by the A / D conversion circuit 42. In other words, the period of the pulse current is preferably related to the period of a digital signal processed in the leakage detection process of the control circuit 50.

[0059] Here, an example of the "period associated with the sampling period" is a period that is twice the period of the sampling performed by the A / D conversion circuit 42. However, the period of the pulse current is not limited to this.

[0060] By making the period of the pulse current twice the period of the sampling, the period of the test signal can be made to correspond to the period of the digital signal processed in the leakage detection process. This allows the control circuit 50 to more accurately distinguish between the test signal derived from the pulse current and the signal derived from the leakage current. This further improves the accuracy of the leakage current interruption test.

[0061] The test coil 140 is a winding wound around the magnetic core 31 of the zero-phase current transformer 30. One end of the test coil 140 is connected to the second main electrode 123 of the pulse current output element 120. In this way, the test coil 140 sequentially acquires a plurality of pulse currents output from the pulse current output element 120. As shown in Fig. 2, the pulse currents S11, S12, S13, ..., S1n sequentially flow through the test coil 140 at time intervals corresponding to, for example, twice the period of the sampling executed by the A / D conversion circuit 42.

[0062] The test coil 140 is wound around the magnetic core 31 at a position different from that of the detection coil 32. That is, the test coil 140 is magnetically coupled to the detection coil 32 via the magnetic core 31. Therefore, as each of the pulse currents S11, S12, S13, . . . , S1n flows sequentially through the test coil 140, a plurality of test currents flow through the detection coil 32. That is, the detection coil 32 detects the test currents.

[0063] When the pulse current flows through the test coil 140, as shown in FIG. 3, a test current having a positive current value (for example, S21, S23, . . . , S2m-1) flows through the detection coil 32 due to a current change in the test coil 140. Also, a test current having a negative current value (for example, S22, S24, . . . , S2m) flows through the detection coil 32 due to a current change in the test coil 140 at the time when each pulse current has finished flowing. As a result, a test current having a positive current value and a test current having a negative current value flow alternately through the detection coil 32. In the case of the example shown in FIG. 3, the test currents flow in the order of test currents S21, S22, S23, S24, . . . S2m-1, S2m. These test currents having positive and negative current values ​​correspond to "test currents induced by the pulse current flowing through the test coil 140".

[0064] The period of the test currents (S21, S22, S23, S24, . . . , S2m-1, S2m) in which test currents having positive current values ​​and test currents having negative current values ​​alternately corresponds to the period of sampling performed by the A / D conversion circuit 42 (period of the digital signal processed in the leakage detection process). Here, the period of the test current corresponds to, for example, the time between the starting point of an arbitrary test current (for example, test current S21 shown in FIG. 3) and the starting point of the next test current (for example, test current S22) (time T2 shown in FIG. 3). However, the period of the test current is not limited to this.

[0065] The detection coil 32 outputs a signal of the detected test current to the amplifier circuit 41. By making the period of the pulse current sufficiently shorter than the period of the leakage current, the detection accuracy of the test current in the detection coil 32 can be improved. This can further improve the accuracy of the earth leakage interruption test. In addition, the amplifier circuit 41 amplifies the signal output from the detection coil 32, and outputs the amplified signal to the A / D conversion circuit 42.

[0066] The A / D conversion circuit 42 performs sampling, quantization, and encoding of the signal corresponding to the test current, and converts the signal corresponding to the test current into a digital signal. As a result, a signal having the same period as the digital signal processed in the leakage detection process is obtained. The obtained signal corresponds to the "test signal." Here, the period of the test signal corresponds to, for example, the time between the starting point of an arbitrary test signal (e.g., test signal S31 shown in FIG. 4) and the starting point of the next test signal (e.g., test signal S32) (time T3 shown in FIG. 4). The digital signal (test signal) obtained by converting the signal of the test current detected by the detection coil 32 (including the signal that has passed through the amplifier circuit 41) is an example of the "second digital signal."

[0067] The A / D conversion circuit 42 outputs a test signal to the control circuit 50. In this way, by making the path of the test current signal derived from the pulse current and the path of the signal derived from the leakage current, which run from the detection coil 32 to the control circuit 50, the same as each other, it is possible to check whether the detection coil 32, the amplifier circuit 41, and the A / D conversion circuit 42 properly fulfill their respective roles in the earth leakage interruption function.

[0068] The control circuit 50 executes a simulation process based on the test signal output from the A / D conversion circuit 42. Examples of the simulation process executed by the control circuit 50 include the following.

[0069] First, the control circuit 50 calculates, for example, a simulated value I that simulates the effective value of a leakage current based on the signal value of each test signal output from the A / D conversion circuit 42. Here, the sequence of test signals is a signal sequence in which positive signals (for example, test signals S31, S33, . . ., S3k-1) and negative signals (for example, test signals S32, S34, . . ., S3k) are alternately arranged in time series, as shown in FIG.

[0070] For example, the control circuit 50 sequentially adds up the absolute values ​​of the signal values ​​of the test signals. For example, if the absolute value of the signal value (S31) of the test signal S31 is |(S31)|, the absolute value of the signal value (S32) of the test signal S32 is |(S32)|, the absolute value of the signal value (S33) of the test signal S33 is |(S33)|, the absolute value of the signal value (S3k-1) of the test signal S3k-1 is |(S3k-1)|, and the absolute value of the signal value (S3k) of the test signal S3k is |(S3k)|, the control circuit 50 calculates [simulated value I=|(S31)|+|(S32)|+|(S33)|+···+|(S3k-1)|+|(S3k)|].

[0071] In this way, the process of adding together the absolute values ​​of the test signals sampled at a specific period corresponds to the process of extracting signals having a specific period from an arbitrary signal sequence by Fourier transform and adding together the signal values ​​of the extracted signals. That is, when calculating the simulation value I, the control circuit 50 can obtain the integrated value of multiple test signals arranged at a specific period without performing a process with a large calculation load such as Fourier transform. As a result, it is possible to reduce the calculation load and calculate the simulation value I that appropriately reflects the effective value of the leakage current.

[0072] However, the method of calculating the simulated value I is not limited to this. For example, the simulated value I may be calculated by calculating the sum of the signal value of the positive test signal and the signal value of the negative test signal multiplied by (-1), such as [simulated value I=(S31)-(S32)+(S33)-..+(S3k-1)-(S3k)].

[0073] Next, the control circuit 50 compares the calculated simulated value I with a threshold value. Here, the threshold value is the same as the threshold value used in the leakage current detection process. The threshold value may correspond to each value of the sensitivity current selected by the sensitivity current changeover switch 55.

[0074] Next, the control circuit 50 compares the simulated value I with the threshold value, and if the simulated value I is equal to or greater than the threshold value, outputs a tripping signal to the tripping unit 60, controlling the tripping unit 60 to cut off the electrical circuit including the power feeders 20a and 20b. On the other hand, if the simulated value I is less than the threshold value, the control circuit 50 does not output a tripping signal. The control circuit 50 executes a simulation process that includes each of these processes. The test tripping operation of the control circuit 50 is an example of a "test tripping".

[0075] The control circuit 50 preferably generates test result information related to the results of the execution of the simulation process. For example, the test result information includes test interruption information when a test interruption is performed and non-interruption test information when a test interruption is not performed as a test result. The control circuit 50 also preferably outputs the generated test result information to the non-volatile memory 52. ​​This allows the non-volatile memory 52 to store the interruption information output from the control circuit 50, distinguishing whether it is an earth leakage interruption or a test interruption. That is, from the interruption information stored in the non-volatile memory 52, the state information of the earth leakage circuit breaker 10 related to the number of earth leakage interruptions, the number of test interruptions, the number of test successes (the number of non-interruption tests), etc. can be grasped, and the information can be used for maintenance information of the earth leakage circuit breaker 10, etc.

[0076] As described above, the embodiment has been described, but the above embodiment is presented as an example, and the present invention is not limited to the above embodiment. The above embodiment can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0077] 10 Earth leakage circuit breaker 20a,20b feeder line 30 Zero phase current transformer 31 Magnetic Core 32 Detection coil 41 Amplification circuit 42 A / D conversion circuit 50 Control circuit 52 Non-volatile memory 55 Sensitivity current changeover switch 60 Tripping section 61 Tripping coil 62 Switch 71 Power supply circuit 110 Test start switch 120 Pulse current output element 130 Current limiting element 140 Test coil

Claims

1. A power supply line connected between a power source and a load; a zero-phase current transformer including a magnetic core and a detection coil wound around the magnetic core to detect a leakage current from the power supply line; an A / D conversion circuit connected to the detection coil and configured to convert a signal of the leakage current detected by the detection coil into a first digital signal; a control circuit that controls earth leakage interruption based on the first digital signal; a pulse current output element that outputs a pulse current with a period different from that of the leakage current; a test coil that is wound around the magnetic core at a position different from that of the detection coil and that passes the pulse current obtained from the pulse current output element; Equipped with The detection coil detects a test current induced by the pulse current flowing through the test coil; the A / D conversion circuit converts the signal of the test current detected by the detection coil into a second digital signal; The control circuit controls a test interruption based on the second digital signal. Earth leakage circuit breaker.

2. 2. The earth leakage breaker according to claim 1, wherein the pulse current output element outputs the pulse current at a period shorter than that of the leakage current.

3. a period of the pulse current corresponds to twice the period of sampling of the first digital signal executed by the A / D conversion circuit; 3. The earth leakage circuit breaker according to claim 1, wherein a period of the test current and a period of the second digital signal correspond to a period of the first digital signal.

4. 3. The earth leakage circuit breaker according to claim 1, wherein the control circuit controls an output operation of the pulse current output element by a drive signal output to the pulse current output element.

5. 3. The earth leakage circuit breaker according to claim 1, wherein the control circuit outputs a tripping signal based on the test tripping when a value obtained by sequentially adding up the absolute values ​​of each signal value in the plurality of second digital signals converted by the A / D conversion circuit is equal to or greater than a threshold value.

6. 3. The earth leakage circuit breaker according to claim 1, wherein the A / D conversion circuit samples the leakage current signal and the test current signal at the same cycle.

7. 3. The earth leakage circuit breaker according to claim 1, further comprising a storage unit that stores each of earth leakage interruption information and test interruption information output from the control circuit.

8. a power supply circuit for converting AC power transmitted from the power supply line into DC power; a current limiting element connected between the power supply circuit and the pulse current output element to limit a current flowing from the power supply circuit to the pulse current output element; The earth leakage circuit breaker according to claim 1 or 2, further comprising:

9. 3. The earth leakage circuit breaker according to claim 1, further comprising a test start switch connected to the control circuit and outputting a test start signal to the control circuit.

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