Apparatus and method for testing the integrity of a ground fault detection device

Abstract

To provide a device and method for testing the integrity of an entire ground fault detection device.SOLUTION: An integrity testing device for a ground fault detection device has a zero-phase current transformer arranged so that an AC line passes through it, an earth leakage relay for the AC line that operates when the output from a secondary winding of the zero-phase current transformer exceeds a predetermined value, and a circuit breaker that interrupts the AC line according to the output of the earth leakage relay. The integrity testing device also includes a test conductor that passes through the zero-phase current transformer or is arranged around the zero-phase current transformer, a portable power source that sends a pseudo-ground fault signal to the test conductor, an ammeter that measures the current value of the pseudo-ground fault signal, and a variable resistance in the circuit so that the portable power source can increase or decrease the alternating current. The integrity testing device preferably includes means for measuring the elapsed time from when the pseudo ground fault signal is issued until when the earth leakage relay outputs the predetermined signal to the circuit breaker.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for taking power from a separate circuit, lowering the voltage below that actually used, and using a pseudo leakage current to check the soundness of the earth fault detection device (between the ZCT and the input side of the earth fault relay) and prevent earth fault accidents. [Background technology]

[0002] In factories that use power sources such as cranes, ground fault accidents are prevented by installing high-voltage panels that step down the transmitted high-voltage AC to the working voltage, air circuit breakers (hereinafter also referred to as ACBs) in the electrical room that supplies power to the factory equipment, and ground fault detection devices in the crane power supply panels.

[0003] 4, a ground fault detection device 1 is usually composed of a zero-phase current transformer 2 (hereinafter also referred to as ZCT) arranged so that an AC circuit passes through it, a ground leakage relay 3 of the AC circuit which operates when the output from the secondary winding of the zero-phase current transformer 2 exceeds a predetermined value, and an overcurrent circuit breaker 4 (hereinafter also referred to as NFB (no fuse breaker)) which serves as a circuit breaker that cuts off the AC circuit in response to the output of the ground leakage relay 3. In general, a test button of the ground leakage relay 3 is used to test whether the output of the ground leakage relay 3 reliably operates the NFB 4 and instantly cuts off the AC circuit.

[0004] If the ground fault detection device did not function properly, the ACB or high-voltage panel would detect a ground fault and cut off the power to the entire factory. This could cause wiring to burn out, or the factory to stop operating, and it could take a long time to restore operations while investigating the cause.

[0005] For example, Patent Document 1 discloses an earth leakage breaker having a dummy current circuit, in which all circuits can be checked using a test button.

[0006] Furthermore, Patent Document 2 discloses a technique for checking the operation of a ZCT by sending a pseudo signal from the earth leakage relay main body to the ZCT. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2007-96616 A [Patent Document 2] JP 2003-274550 A Summary of the Invention [Problem to be solved by the invention]

[0008] The above conventional techniques have the following problems. The technology described in Patent Document 1 is related to an earth leakage circuit breaker and cannot be applied directly to an earth fault detector. In addition, the technology described in Patent Document 2 uses the secondary winding of the ZCT, and there is a problem in that it is not possible to confirm whether the ZCT can reliably detect an earth fault in an AC circuit. In other words, it is not possible to inspect from the ZCT to the input side of the earth leakage relay. Furthermore, with conventional inspections, it is not possible to grasp the time from the occurrence of an earth fault to the interruption of the AC circuit.

[0009] The present invention has been made in consideration of the above circumstances, and has an object to provide an apparatus and method for testing the soundness of the entire ground fault detection apparatus, from the ZCT to the earth leakage relay input side. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems and achieve the object, the present invention provides a soundness test device for a ground fault detection device, which comprises a zero-phase current transformer arranged so that an AC circuit passes through it, a leakage current relay for the AC circuit that operates when the output from the secondary winding of the zero-phase current transformer exceeds a predetermined value, and a circuit breaker that cuts off the AC circuit in accordance with the output of the leakage current relay, and is characterized in that it comprises a test wire that passes through the zero-phase current transformer or is wrapped around the zero-phase current transformer, a portable power source that sends a pseudo-earth fault signal through the test wire, and an ammeter that measures the current value of the pseudo-earth fault signal, and has a variable resistor in the circuit so that the portable power source can increase or decrease the AC current.

[0011] Furthermore, it is considered that a more preferable solution would be for the health test apparatus for a ground fault detection device of the present invention to further include a means for measuring the elapsed time from when the pseudo-ground fault signal is issued to when the earth leakage relay outputs a specified signal to the circuit breaker.

[0012] In order to solve the above-mentioned problems and achieve the object, the present invention provides a method for testing the health of a ground fault detection device comprising a zero-phase current transformer arranged so that an AC circuit passes through it, a leakage current relay for the AC circuit that operates when the output from the secondary winding of the zero-phase current transformer exceeds a predetermined value, and a circuit breaker that cuts off the AC circuit in accordance with the output of the leakage current relay, characterized in that a test conductor is arranged so as to pass through the zero-phase current transformer or to be wrapped around the zero-phase current transformer, and an AC current is passed through the test conductor from a portable power source while increasing the current value as a pseudo-ground fault signal, and the health of the device is judged by whether the leakage current relay outputs a predetermined signal to the circuit breaker when the pseudo-ground fault signal is passed at a predetermined current value.

[0013] The method for testing the soundness of a ground fault detection device according to the present invention includes the steps of: (a) determining whether the fault is sound or not based on whether a time elapsed from when the pseudo earth fault signal having a predetermined current value is generated until when the earth leakage relay outputs a predetermined signal to the circuit breaker is within a predetermined time; (b) confirming in advance that the pseudo earth fault signal outputs a predetermined current value; This is thought to be a more preferable solution. Effect of the Invention

[0014] According to the present invention, the soundness test device and method for the earth fault detection device can test the soundness of the whole earth fault detection device, and can prevent earth fault accidents caused by failure of the earth fault detection device, thereby suppressing serious troubles caused by earth faults. In addition, when replacing the earth fault detection device's earth leakage relay or ZCT, it is possible to confirm that they are working properly. [Brief description of the drawings]

[0015] [Figure 1] 1 is a circuit diagram showing a schematic configuration of a soundness test device for a ground fault detection device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a detailed schematic diagram showing a device configuration of the soundness test device for the ground fault detection device according to the embodiment. [Diagram 3] 11 is a graph showing the measurement results of the elapsed time from issuing a pseudo-earth fault signal to interrupting the AC circuit using the soundness test device for the earth fault detection device of the above embodiment, where (a) shows an example of the operation of the earth fault detection device in the machine side distribution board, and (b) shows an example of the operation of the ACB in the electrical room. [Figure 4] FIG. 1 is a circuit diagram showing a schematic configuration of a conventional ground fault detection device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, the embodiments of the present invention will be described in detail. Note that the drawings are schematic and may differ from the actual ones. Furthermore, the following embodiments are merely examples of devices and methods for embodying the technical idea of ​​the present invention, and are not intended to limit the configuration to the following. In other words, the technical idea of ​​the present invention can be modified in various ways within the technical scope described in the claims.

[0017] First, the configuration of a soundness test device for a ground fault detection device according to an embodiment of the present invention will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a circuit diagram showing the schematic configuration of a ground fault detection device and a test device. Fig. 2 is a detailed schematic diagram of the configuration of the test device.

[0018] The ground fault detection device 1 consists of a ZCT 2, a leakage current relay 3, and an NFB 4 as a circuit breaker for the AC circuit. The NFB 4 and ZCT 2 are arranged in this order from the power supply side 5 of the AC circuit to the power receiving side 6 of a crane or the like. The output of the secondary winding of the ZCT 2 is connected to the input terminal of the leakage current relay 3. When a ground fault occurs in any of the phases of the interphase current of a three-phase AC that is normally balanced, an excessive current flows in that phase. The ZCT 2 detects the AC magnetic field generated by the excessive current and outputs to the leakage current relay 3, which then outputs to the NFB 4 to cut off the AC circuit.

[0019] The test device 10 of this embodiment includes a test lead 11 arranged to pass through the ZCT 2, a portable power source 20 for passing an AC current through the test lead 11, and an ammeter 12 for measuring the current value passed through the test lead 11. In this embodiment, a stopwatch 30 is also provided as a measuring means for measuring elapsed time. The test lead 11 may be arranged so as to be wound around the ZCT 2 multiple times. For example, it is preferable to store the portable power source 20, the ammeter 12, and the measuring means 30 for elapsed time together in a portable case or the like. It is also preferable to store the test lead 11 in the case.

[0020] The portable power source 20 of this embodiment has a DC power source 21 such as a dry cell, a start switch 22, a start LED 23 for confirming start, a sine wave inverter 24 for converting DC electricity to AC electricity, a transformer 25 for converting AC voltage to a predetermined output voltage, an electric resistor 26 and a variable resistor 27 for adjusting the output current to a predetermined value, a fuse 28, and a connector 29 for connecting to the test lead 11. It also has a push button 7 for issuing a ground fault signal midway through the output to the test lead 11 and an ammeter 12. For example, the DC voltage can be DC 12 V, the output of the sine wave inverter 24 can be AC ​​100 V, the output voltage to the test lead 11 can be AC ​​17 V, and the electric resistor 26 can be 20 Ω, so that the output current can be a maximum of 0.85 A. The variable resistor 27 arranged in series with the electric resistor 26 can increase or decrease the current value flowing through the test lead 11.

[0021] The stopwatch 30 of this embodiment has a start / stop terminal 30 that constitutes a circuit for starting and stopping time measurement, and a reset / wrap terminal 32 that constitutes a circuit for measuring and resetting time. The circuit for starting and stopping time measurement also has a push button 7 that is linked to a pseudo ground fault signal. The reset / wrap terminal 32 is connected to the output terminal of the earth leakage relay 3 by a connector 34. The stopwatch 30 can also be reset by a reset push button 33. One of the connectors 34 may be an alligator clip.

[0022] A method of testing the soundness of the ground fault detection device 1 using the above-mentioned test device 10 will be described. Since the inspection of the earth leakage relay 3-NFB 4 can be performed using the existing circuit, the description will be omitted.

[0023] To construct the test circuit, the test lead 11 is set so as to pass through ZCT2. It may be wound around ZCT2 multiple times. Next, both ends of the test lead 11 are connected to the connector 29 of the portable power supply 20. The connector 34 of the circuit of the reset / wrap terminal 32 of the stopwatch 30 is connected to the output terminal of the earth leakage relay 3.

[0024] The start switch 22 of the portable power source 20 is connected, and the start LED 23 is confirmed to be lit. While pressing the push button 7 for issuing a pseudo earth fault signal, the variable resistor 27 is operated to increase the output current flowing through the test lead 11 . The earth leakage relay 3 outputs a ground fault detection signal to the NFB 4, and the NFB 4 checks the current value at which it cuts off the AC circuit. If this current value exceeds a specified current value, or if the earth leakage relay does not activate even when the current value exceeds the specified current value, it is determined that there is a defect between the ZCT 2 and the earth leakage relay 3, and the required measures are taken. For example, a check is made for broken wires, and the ZCT 2 and earth leakage relay 3 are replaced. The above-mentioned specified current value is a set value of an arbitrary current that is detected as an earth leakage current by each circuit breaker. For example, if there is an abnormality in the detection by the NFB, the ACB or high-voltage panel may detect a ground fault, which may result in cutting off the power to the entire factory, burning the wiring, or causing factory operations to halt.

[0025] If the current value at which the earth leakage relay 3 operates is within a predetermined value, the variable resistor 27 is fixed to that current value. First, the start switch 22 of the portable power source 20 is released, and it is confirmed that the start LED 23 is turned off. A reset push button 33 resets the stopwatch 30 . Reinstate NFB4. Once again, the start switch 22 of the portable power source 20 is connected, and it is confirmed that the start LED is lit. The push button 7 for the pseudo earth fault signal is pressed, and the elapsed time until the NFB 4 is disconnected is measured with the stopwatch 30. If the elapsed time is within a predetermined value, the ground fault detection device 1 is determined to be normal.

[0026] FIG. 3 shows the measurement result of the elapsed time using the test device of this embodiment. In the example of FIG. 3(a), the NFB4 cuts off the AC circuit when the output current to the test lead 11 is 0.2 A. The operating time of this earth fault detection device is 0.1 s, which is shorter than the operating time until the ACB in the upstream electrical room is activated and cuts off the power supply, or the operating time until the power supply of the high-voltage panel is cut off. In a sound earth fault detection device, the NFB4 cuts off the AC circuit at a circle (solid line) within the detection setting value after issuing a pseudo earth fault signal. On the other hand, the one shown by the cross (broken line) is longer than the time when the ACB or high-voltage panel is activated, and the earth fault detection device 1 is determined to be defective. Note that the operating time of the earth fault detection device 1, 0.1 s, is an example of the operating time specified by the earth leakage relay. If the time until actual detection is longer than the operating time, the circuit breaker of the upstream ACB or high-voltage panel will be activated, leading to a power outage in the entire factory. The purpose of this test equipment and test method is to confirm that earth fault detection works within this operating time. The operating time of this earth fault detection device is preferably set to the operating time specified in JIS C8374:1991, the standard for earth fault relays, specifically, fast type: within 0.1 s, time delay type: over 0.1 s within 2 s, and inverse time type: operating time determined by the rated sensitivity current and its multiples. Note that this test equipment and test method are preferably applied not only to the inspection of existing earth fault detection devices, but also when replacing ZCT2, earth fault relay3, and NFB4.

[0027] In the above embodiment, an overcurrent circuit breaker, i.e., an NFB, has been used as an example of the circuit breaker of the ground fault detection device, but the present invention can also be applied to the case where the circuit breaker is an air circuit breaker, i.e., an ACB, as shown in Fig. 3(b). The portable power source, ammeter, resistor, variable resistor, etc. can be changed to those with the desired capacity according to the operating current setting value and the specified operating time of the ACB. [Industrial Applicability]

[0028] According to the earth fault detection device soundness test apparatus and soundness test method of the present invention, it is possible to test the soundness of the entire earth fault detection device, and thus it is possible to prevent earth fault accidents due to missed earth fault detection caused by a malfunction of the earth fault detection device, and it is possible to suppress serious troubles caused by earth faults, thereby contributing to improved productivity and being industrially useful. [Explanation of symbols]

[0029] 1. Earth fault detection device 2 Zero phase current transformer (ZCT) 3. Earth leakage relay 4. Overcurrent Breaker (NFB) 5 Power supply side 6. Receiving side 7 Push button (PB1) (linked) 10 Test Equipment 11 Test Leads 12 Ammeter 20 Portable power supply 21 DC power supply (batteries) 22 Start switch 23 Start LED 24 Sine wave inverter 25. Transformer 26 Electrical Resistors 27 Variable Resistor 28 Fuse 29 Connectors 30 Time measurement means (stopwatch) 31 Start / Stop Terminal 32 Reset / wrap terminal 33 Reset push button 34 Connector

Claims

1. a zero-phase current transformer arranged so that an AC current path passes through the zero-phase current transformer; a leakage current relay for the AC circuit that operates when an output from a secondary winding of the zero-phase current transformer exceeds a predetermined value; A soundness test device for a ground fault detection device comprising: a circuit breaker that interrupts the AC circuit in response to an output of the earth leakage relay, a test lead disposed to pass through the zero-phase current transformer or to be wound around the zero-phase current transformer; a portable power source for applying a simulated earth fault signal to the test lead; an ammeter for measuring a current value of the pseudo ground fault signal; a portable case for housing the portable power source, the ammeter, and the test leads; The portable power source has a variable resistor in a circuit so that the AC current can be increased or decreased. A device for testing the integrity of earth fault detection devices.

2. 2. The soundness test device for a ground fault detection device as described in claim 1, further comprising a means for measuring the elapsed time from when the pseudo ground fault signal is issued to when the earth leakage relay outputs a predetermined signal to the circuit breaker, the means for measuring the elapsed time being capable of being housed in the case.

3. a zero-phase current transformer arranged so that an AC current path passes through the zero-phase current transformer; a leakage current relay for the AC circuit that operates when an output from a secondary winding of the zero-phase current transformer exceeds a predetermined value; A method for testing the soundness of a ground fault detection device comprising: Carry the case containing the portable power source, the ammeter, and the test lead to the ground fault detection device, A test lead is arranged so as to pass through the zero-phase current transformer or to be wound around the zero-phase current transformer; Passing an AC current from a portable power source through the test conductor while increasing the current value as a pseudo-earth fault signal; A method for testing the health of a ground fault detection device, in which the health of the device is judged by whether the earth leakage relay outputs a predetermined signal to the circuit breaker when the pseudo ground fault signal is passed at a predetermined current value.

4. The method for testing the integrity of a ground fault detection device as described in claim 3, further comprising determining whether the device is healthy by determining whether the elapsed time from when the pseudo ground fault signal of a predetermined current value is issued to when the earth leakage relay outputs a predetermined signal to the circuit breaker is within a predetermined time.

5. 5. The method for testing the soundness of a ground fault detection device according to claim 3, further comprising the step of confirming in advance that the portable power source outputs a predetermined current value as the pseudo ground fault signal.

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