JPH0739251U - Artificial ground fault test equipment - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an artificial ground fault tester which can be formed to be extremely simple, inexpensive, small and lightweight without using special parts, and which can generate a nearly complete ground fault. [Structure] A series circuit of a variable resistor 38 and an ammeter 39 for measuring a ground fault current is provided between the load-side one phase of the test distribution line circuit breaker 4 of the ungrounded high-voltage distribution system and the ground, and a variable circuit is provided. Resistance 3
By the operation of 8, a ground fault is artificially generated.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an artificial ground fault test apparatus that artificially causes a ground fault in an ungrounded high voltage distribution system and measures the ground fault current.

[0002]

[Prior art]

 Conventionally, an artificial ground fault tester used to test an ungrounded high voltage power distribution system as an in-house equipment for a customer of special high voltage power reception or high voltage power reception measures an earth fault current by artificially generating a ground fault. Based on this measurement result, it is verified whether or not the distribution line circuit breaker of the system operates normally, and the system is configured as shown in FIG.

FIG. 2 shows a case where the secondary side of extra-high-voltage power reception is an ungrounded high-voltage power distribution system of 6600 V or 3300 V, and the three-phase high-voltage power source on the secondary side (load side) of the power receiving transformer 1 connects the main circuit breaker 2. Power is supplied to the three-phase high-voltage bus bar 3 via.

Further, the three-phase power source of the bus bar 3 is branched and fed to the three-phase distribution lines 6, 7 via the distribution line breakers 4, 5, and the power sources of the distribution lines 6, 7 turn on the switches 8, 9. The power is supplied to the load via. Further, the primary side of the ground-type instrument transformer 11 is connected to the high-voltage bus bar 3 via a disconnector 10 with a fuse, and the limiting resistance 12 and the ground fault are connected between both ends of the ground-type instrument transformer 11 on the tertiary side. A voltmeter 14 and a ground fault overvoltage relay 15 are provided in parallel.

When a ground fault occurs on the distribution lines 6 and 7, the zero-phase current transformers 16 and 17 of the distribution lines 6 and 7 detect the zero-phase current, and the ground-fault overvoltage relay 15 operates. Only at this time, the ground fault relays 18 and 19 operate and the circuit breakers 4 and 5 are accidentally tripped and opened. In the figure, 20 is a voltmeter connected to the secondary winding of the grounded voltage transformer 11 via a voltmeter changeover switch, 21 is a DC operation busbar, and 22 and 23 are circuit breakers 4 and 5. The external coils 24 and 25 are impedance boxes.

Next, when the circuit breaker 4 is tested as a test distribution line circuit breaker, the artificial ground fault test apparatus 26 is connected to the R phase on the load side of the circuit breaker 4, for example.

This conventional test device 26 includes a closing switch 27, a parallel circuit of a resonance prevention resistor 28 and a disconnector 29, and a test transformer 30 between the R-phase end of the circuit breaker 4 and the ground. A primary side and a parallel circuit of a primary side measuring ammeter 31 and a disconnector 32 are provided in series, and a measuring voltmeter 33 is provided between both ends of the secondary side of the transformer 30. A series circuit including a NIF switch 34, a secondary-side measuring ammeter 35, and a water resistor 36 is installed in parallel. The transformer 30 has a capacity of, for example, about 6600V / 210 to 105V, 5 to 20KVA.

Before the test, the disconnector 29 is open and the disconnector 32 is closed. After confirming that the transformer 30 is in the no-load state, turn on the switch 27 and open the disconnector 32, and there is no risk of resonance due to the ground capacity of the entire system and the inductance of the transformer 30. After confirming that, the disconnector 29 is closed and the resistor 28 is short-circuited.

Next, the switch 34 is closed and injected into the water resistor 36 to gradually reduce the resistance value thereof and gradually reduce the impedance between the R phase of the system and the ground. When a ground fault is artificially generated in the system due to the decrease in the impedance, the ground fault overvoltage relay 15 and the ground fault direction relay 18 operate, and the distribution line disconnector 4 trips due to an accident.

Then, the operation sensitivity of the distribution line 6 is determined by the ammeters 31 and 35 at the operating points of the relays 15 and 18, the measured values of the voltmeter 33, the indicated value of the ground fault voltmeter 14 of the system, and the like. Detects and confirms to determine whether the operation is normal or abnormal. Further, the test is repeated in the state where the resistance value of the water resistor 36 is further reduced, and the inoperative state of the other circuit breaker 5 when the ground fault current increases is also confirmed.

Then, it is verified whether the operation functions of the system such as the circuit breakers 4 and 5 are normal based on the determination results. In addition, the operating status of each relay will be verified by calculations using the results of ground fault current and voltage measurements. When the test is completed, the test device 26 is disconnected from the system.

[0012]

[Problems to be solved by the device]

 In the case of the conventional artificial ground fault test apparatus 26 of FIG. 2, a test transformer 30, a water resistor 36, a plurality of meters 31, 33, 35 and a plurality of switchgear devices 27, 29, 32, 34 are required. Complex, large and expensive. Moreover, since the transformer 30 and the water resistor 36 are required, the weight is large and it is not easy to transport to the test site.

Further, the water resistor 36 is a special component, cannot be easily obtained, and is not easily manufactured. Further, even if the resistance value of the water resistor 36 is set to zero, since the impedance of at least the transformer 30 exists between the grid and the ground, a complete ground fault cannot be realized, and conventionally, the cable of the grid is not able to be realized. There is a problem in that the ground capacity of the entire system can only be calculated and estimated from the type and length, and the ground capacity cannot be accurately determined.

The present invention takes advantage of the extremely high impedance to ground of this type of ungrounded high-voltage power distribution system in Japan, and can be made extremely simple, inexpensive, compact, and lightweight without the use of special parts, and The purpose is to provide a testing device capable of generating a nearly complete ground fault.

[0015]

[Means for Solving the Problems]

 In order to achieve the above object, in the artificial ground fault test apparatus of the present invention, a variable resistance and a ground fault are connected between the load-side one phase of the test distribution line circuit breaker of the ungrounded high-voltage distribution system and the ground. A series circuit with an ammeter for current measurement is provided, and the resistance value of the variable resistor is set to artificially generate a ground fault.

[0016]

[Action]

 In the artificial ground fault tester of the present invention configured as described above, it is possible to form an extremely simple, inexpensive, small and lightweight device by using only a variable resistance and an ammeter without using special parts such as a water resistor. To be done. Then, if the resistance value of the variable resistor is set to zero, an almost complete ground fault can be realized in the system, the ground capacity of the entire system can be accurately obtained based on the measurement results, and the test performance improves.

[0017]

【Example】

 An example will be described with reference to FIG. 1, the same reference numerals as those in FIG. 2 indicate the same or corresponding ones, and a different point is that an artificial ground fault test device 37 is provided instead of the test device 26 of FIG.

This test device 37 has a series circuit of a variable resistor 38 and an ammeter 39 for measuring a ground fault current between the R phase on the load side of the circuit breaker 4 which is the test distribution line circuit breaker and the ground. It is provided and formed. The variable resistor 38 is formed of, for example, a single metal winding type variable resistor or a enamel resistor.

Further, the ammeter 39 makes it possible to measure easily, for example, when the demand time is a prescribed response time until the ground fault overvoltage relay 15 and the ground fault direction relay 18 operate and the breaker 4 is tripped. It is formed by the highest indicated demand ammeter set within. The ammeter 39 is provided on the ground side by the variable resistor 37 in order to reduce the ground potential of the ammeter 39 to ensure the safety of measurement.

At the time of the test, the circuit breaker 4 is opened, the test device 37 is connected to the system 3 as shown in FIG. 1, the variable resistance 38 is set to the maximum resistance value, and then the circuit breaker 4 is closed. At that time, the measured values of the ammeter 39 and the ground fault voltmeter 14 are read.

At this time, if the ground fault overvoltage relay 15 and the like operate normally, the relay 15 and the ground fault direction overcurrent relay 18 operate to open the circuit breaker 4. Then, the operation sensitivity and the like of the relay 4 are detected and confirmed by the measured values of the ammeter 39 and the ground fault voltmeter 14 at the time of operation of the relays 15 and 18, respectively.

Further, the variable resistor 38 is operated to further reduce its resistance value, the ground fault current is increased stepwise, and the test is repeated to confirm the inoperative state of the circuit breaker 5 and the like. At this time, in order to obtain the ground capacity of the entire system, the variable resistance 38 is operated to make the resistance value to the minimum (zero) and the test is performed.

Then, based on the measured value (actual value) of the ammeter 39 at this time, the actual ground capacity of the entire system can be accurately obtained from the calculation, not by the conventional estimation from the type and length of the cable. You can Since the actual ground capacity of the entire system can be obtained, it is also possible to back-calculate the detection sensitivity of the ground fault relay from this capacity and perform verification tests of its operation and non-operation.

Since the ungrounded system 3 has an extremely high ground impedance, even if an artificial ground fault is generated, only the movement of the potential occurs, and the amount of current flowing through the test device 37 to the ground is small and the safety is high. It will not be damaged. Further, since the ground fault current flows for only a few seconds, the variable resistor 38 can be formed of a small resistor with relatively small power consumption, such as a variable resistor of 0 to 2000 Ω3A capable of conducting for 5 seconds.

Since the test device 37 is formed by providing only the variable resistor 38 and the ammeter 39 which are general-purpose products, it is much simpler, cheaper, smaller, and lighter than the conventional device, and is extremely transportable to the site. Easy to do. By the way, although the test device 37 is provided between the R phase on the load side of the circuit breaker 4 and the ground in the above embodiment, it may be provided between the other phase on the load side of the circuit breaker 4 and the ground. Also, the test distribution line circuit breaker may be other than the circuit breaker 4, as a matter of course.

[0026]

[Effect of device]

 Since the present invention is configured as described above, it has the following effects. Since the series circuit of the variable resistor 38 and the ammeter 39 for ground fault current measurement is provided between the load-side one phase (R phase) of the test distribution line circuit breaker 4 and the ground, the water resistance Without using special parts such as vessels, it is possible to use general-purpose parts that are easily available, extremely simple, inexpensive, compact, lightweight, and easy to form.

Further, if the resistance value of the variable resistor 38 is set to zero, the ground capacity of the entire system at the time of a complete ground fault can be accurately obtained based on the measurement result, and the test performance is improved.

[Submission date] February 4, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

Next, the switch 34 is closed and injected into the water resistor 36 to gradually reduce the resistance value thereof and gradually reduce the impedance between the R phase of the system and the ground. When a ground fault is artificially generated in the system due to the decrease in the impedance, the ground fault overvoltage relay 15 and the ground fault direction relay 18 operate, and the distribution line breaker 4 trips due to an accident.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

Then, it is verified whether the operation functions of the system such as the circuit breakers 4 and 5 are normal based on the determination results. In addition, ground fault current, Ri by the measurement results of the voltage, to verify the operation status of each relay. When the test is completed, the test device 26 is disconnected from the system.

[Brief description of drawings]

FIG. 1 is a connection diagram of an embodiment of an artificial ground fault test apparatus of the present invention.

FIG. 2 is a connection diagram of a conventional device.

[Explanation of symbols]

 3 High voltage busbars 2, 4, 5 Circuit breakers 6, 7 Distribution line 38 Variable resistance 39 Ammeter for ground fault current measurement

Claims (1)

[Scope of utility model registration request] 1. A series circuit of a variable resistor and an ammeter for measuring a ground fault current is provided between a load-side one phase of a test distribution line circuit breaker of an ungrounded high-voltage distribution system and an earth ammeter for measuring the ground fault current. An artificial ground fault test device that artificially generates a ground fault by operating the resistance.