JPH0619400B2 - Distribution line artificial ground fault tester - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a distribution line artificial ground fault tester for instantaneously grounding a distribution line to measure ground line characteristics and perform an operation test of a ground fault protection relay. It is a thing.

[Conventional technology]

Conventionally, when a ground fault occurs in a distribution line, the ground fault protection relay (hereinafter, also simply referred to as a relay) is used to cut off the fault circuit and disconnect it from a sound circuit.
The magnitude of the zero-phase voltage and ground fault current generated in the case of a ground fault depends on the line characteristics that are determined by the line length, etc., so the relay settling, that is, the setting of the relay operating value, should be made according to each line characteristic. There is a need to do.

However, since it is extremely difficult to accurately calculate the ground admittance required for relay settling, it is currently difficult to artificially ground the line to determine the relay operating value based on the ground-fault line characteristics obtained by actual measurement. That's the way it is done. Generally, a test transformer (distribution transformer 6.6k
V) to artificially ground each distribution line and adjust the water resistor connected to the secondary side of the test transformer to adjust the ground fault current, while ground fault resistance-ground fault voltage and ground fault voltage -The line characteristic is obtained by actually measuring the ground fault current characteristic at several points, and the operating value of the relay is determined based on the characteristic.

An example of a test circuit used in such an artificial ground fault test is shown in FIG. The test circuit shown is configured to measure the line characteristics of the distribution line connected to the 6kV bus of the distribution system via the circuit breaker CB and the disconnectors DSa and DSb.
Use switching busbars for safety of measurement work. Based on the measurement result, the operating point (sensitivity) of the ground fault direction relay DG and the ground fault overvoltage relay OVG for operating the circuit breaker CB is set. In the figure, reference numeral 30 is a connecting rod, 31 is a water resistor, 32 is a test transformer (pole transformer), 33 is an iron resonance resonance suppression control resistor, AS (OS) is a high-voltage switch, and FDS is a disconnecting circuit with a fuse. , Vo is a voltmeter for measuring zero-phase voltage, Ph is a phase meter, Vg is a voltmeter for measuring ground fault voltage, Ig is an ammeter for measuring ground fault current, and GPT is a transformer for grounding type instrument.

Explaining the measurement operation, first, circuit breaker CB and disconnector DS
a and DSb are turned on, and the distribution line is in a power transmission state. In addition, disconnectors DSa and DSi and high-voltage switch AS are opened, fused disconnector FDS is turned on, and water resistor 31 has one electrode plate extracted from water (maximum resistance value). In this state, the test rod 30 is brought into contact with the phase wire (T phase in the case shown) of the switching bus bar to be tested, and the disconnector DSc (t) of that phase is turned on. Then, turn on the high-voltage switch AS to generate an artificial ground fault, and turn on DSi to bypass the suppression resistor 33,
Adjust the water resistance in this state (reduce the resistance value from the maximum value gradually), and set the indicated values of Vg, Vo, Ig, Ph including the operating points of the ground fault direction relay DG and the ground fault overvoltage relay OVG. Measure and record at several points.

[Problems to be Solved by the Invention]

However, the above-mentioned conventional artificial ground fault test has the following problems, and in the electric power industry and the like, development of an apparatus that solves these problems has been demanded.

The weight of the test equipment is heavy and the circuit assembly at the measurement site is complicated, which makes the handling very difficult.

Since the fine adjustment of the water resistor is required, the time for which the ground fault current flows is relatively long, and the reliability of protection is reduced due to the fact that the ground fault protection relay cannot be used during that time.

Measures to prevent abnormal voltage due to ferroresonance of test transformer are required.

More specifically, as described above, in the method of causing an artificial ground fault using a pole transformer or water resistance, and measuring the line characteristics of the distribution line or the operating point of the DG relay with a voltmeter or ammeter,
Since a very heavy pole transformer is required and the ground fault resistance is variably adjusted by the water resistance, it is necessary to visually measure the constantly changing voltage and current, which requires a lot of time for preparation and measurement. In addition, there is a risk of abnormal voltage generation due to abnormal resonance that is estimated to be caused by the inductance of the transformer and the ground capacitance of the distribution line.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an artificial ground fault test that does not require a test transformer, is light in weight, and has a simplified device configuration. An object of the present invention is to provide an electric wire artificial-fault test device to semi-automatically perform an artificial ground-fault test, to reduce the amount of work, shorten the test time, and prevent danger.

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides a distribution line artificial ground fault tester for instantaneously artificially grounding a distribution line to measure a ground line characteristic and perform an operation test of a ground fault protection relay: opening and closing of a ground fault device. A ground fault device control unit that performs control; a measurement unit that performs high-speed sampling of zero-phase voltage, ground fault current, etc .; generates a simulated zero-phase voltage and a simulated ground fault current as a test signal of the ground fault protection relay, A relay test circuit section for measuring the operating value of the protection relay; controlling each of the above sections, performing a predetermined calculation on the output data of the measuring section, and performing the ground operation of the line which is the basic data for generating the test signal. And a microcomputer section for obtaining the junction characteristic.

[Action]

The node constants of a power distribution system in which the neutral point is an ungrounded system, that is, the three-phase collective balanced admittance ₀₀ and the three-phase collective unbalanced admittance ₀₀ ′ are given by the following equations and with the ground fault resistance value as R _g . Further, the zero-phase voltage ₀ and the ground fault current at the time of one-line ground fault are given by the following equations and, respectively.

However, _n0 : residual zero-phase voltage when there is no ground fault _n : zero-phase voltage when grounded by an arbitrary resistance (R _g ) E: phase voltage: coefficient that differs depending on the ground fault phase; 1 for R-phase ground fault , S phase ground fault With T phase ground fault That is, by measuring the residual zero-phase voltage _n0 always system, then allowed to ground any phase in the ground fault resistor R _g, zero-phase voltage at the _n
The line constant can be obtained by measuring The distribution line artificial ground fault test apparatus of the present invention having the above-mentioned configuration performs artificial ground fault for a short time by the fixed resistor of the ground fault device, and from the data obtained as a result, calculates the ground fault characteristic of the system by calculation. In addition, the relay operation test is performed by utilizing the characteristics.

More specifically, under the control of the microcomputer, the ground fault device control unit momentarily closes the ground fault device to artificially ground the line, and measures the zero-phase voltage and ground fault current at the time of the ground fault. High speed sampling by. The microcomputer unit inputs the data obtained by this sampling, calculates the ground fault characteristic of the line by performing the operation based on the above formula or formula, and relays the ground fault characteristic based on the ground fault characteristic thus obtained. A simulated zero-phase voltage and a simulated ground fault current are supplied from the test circuit section to the ground protection relay, and the operating value of the ground fault protection relay is measured by the response.

The distribution line ground fault test apparatus of the present invention is measured as described above,
Since data recording, calculation, and other processing can be instantaneously performed, the artificial ground fault can be performed by a heavy pole transformer or a fixed resistor composed of a pure resistance component instead of a water resistance.

〔Example〕

An embodiment of the distribution line artificial ground fault device of the present invention will be described below with reference to FIGS. 1 and 2.

In the distribution line artificial ground fault testing apparatus 1 of the embodiment shown in FIG. 1, the measuring unit 11 includes an input converter 111, n pieces of tarta 112 _i (i = 1 to n) connected in parallel with each other, and each of these. each filter 112 _i connected n pieces of sample and hold (S
/ H) circuit 113 _i (i = 1 to n), a multiplexer 114 and an analog-digital (A / D) converter 115. Further, the relay test circuit 12 includes an input / output switch 121, a voltage amplifier 1
22, an amplitude adjuster 123, a phase adjuster 124, a digital input / output device 125, a sine wave generator 126, an amplitude adjuster 127 and a current amplifier 128, and the microcomputer unit is a microprocessor (CPU) 15 and a data memory 16 And a program memory 17.

The device further includes a ground fault device controller 14 including a digital input / output device 141 and a relay driver 142, an interface (I / F) device 131, a printer 132, a liquid crystal display device (LC).
D) Data input / output unit 13 including 133 and keyboard 134
And a power supply device 18 is provided. The artificial ground fault test apparatus of this embodiment has a high-voltage switch (ground fault device) 2 having a contact rod 20.
Used together with the high-voltage switching unit 2 is a 7.2kV vacuum circuit breaker VCB,
It consists of 8kΩ fixed resistor for ground fault RO, current transformer CTO and protective power fuse PF.

The input converter 111 of the measuring unit 11 is a ground type instrument transformer.
The line voltage and the ground voltage are input from the secondary side X of the GPT, and the ground fault current Ig is input from the current transformer CTO of the high voltage switching unit 2. Note that the filter 112 _i and the sample hold (S /
H) A plurality (n) of series circuits of the circuit 113 _i are provided in parallel because a plurality of measurement elements such as three-phase voltage, zero-phase voltage, and ground fault current are simultaneously sampled at different measurement points, This is so that the data sampled at the same time can be converted into digital data by the A / D converter 115. Further, the input / output switch 121 of the relay test circuit unit 12
Is the zero-phase voltage Vo from the tertiary side Y of the ground type instrument transformer GPT.
However, the secondary current ig is input from the secondary side of the zero-phase current transformer ZCT, and the contact operation signal is input to the digital I / O device 125 from the ground fault direction relay DG or the ground fault overvoltage relay OVG.

Measurement is done by microcomputer (CPU15, data memory
16, under the control of the program memory 17), it is performed at high speed including the phase angle in addition to the voltage and current. Therefore, the time of ground fault due to the pure resistance (fixed resistor RO) of the high-voltage switch 2 is extremely short, about 0.5 seconds. The phase voltage, the ground fault current, the zero phase current, the zero phase voltage and the phase angle between them are measured by an artificial ground fault due to the pure resistance of the high voltage switching unit 2, and the microcomputer unit calculates based on these measured data. Find the parameters (admittance, etc.) of the distribution line. The distribution line characteristics are calculated by admittance calculation using the parameters thus obtained. Further, based on the calculation result, the ground fault current, the zero-phase current, the zero-phase voltage, and the phase angle between them in an arbitrary ground fault resistance are obtained.

Then, the continuous zero-phase current when assuming that the ground fault resistance is gradually decreased from the high resistance value, the zero-phase voltage and the phase angle between them are calculated, and the actual zero-phase current,
The test signal corresponding to the zero-phase voltage is generated by the relay test circuit unit 12 under the control of the microcomputer unit, and in addition to the DG relay or OVG relay under test, the operating point or response operation of these relays is confirmed. Therefore, in the artificial ground fault test, it is not necessary to actually perform the relay operation confirmation test by gradually changing the ground fault resistance.

In the above-mentioned parameter measurement of the distribution line, ground fault current, zero-phase current, zero-phase voltage, the phase angle between them, admittance and the like are displayed on the screen of the LCD 133 of the data input / output unit 13, and These data can be printed out by the printer 132. Also, in the DG or OVG relay test, the data of the relay operating point is displayed,
Printed out.

Next, an example of measurement and test operation by the artificial ground fault test apparatus of this embodiment will be briefly described with reference to FIG.

First, the circuit breaker CB and the disconnectors DSa and DSb are in the closing positions, the distribution line is in the power transmission state, the circuit breaker DSc is open, and the switching bus is in the non-power transmission state. Also, the vacuum circuit breaker VC of the high-voltage switching unit 2
B is open. To carry out the test, the grounding rod 20 connected to the high-voltage switching unit 2 is brought into contact with the phase wire to be tested (T phase in the figure) of the switching busbar, and the disconnecting switch DSc (t) of that phase is turned on. When the test start push button (not shown) of the artificial ground fault test apparatus 1 is pressed in this state, the digital input / output device 14 of the ground fault device control unit 14 is controlled under the control of the microcomputer unit.
A short-time closing signal is sent to the vacuum circuit breaker VCB of the high-voltage switching unit 2 through the relay driver circuit 142 and the relay driver circuit 142, and the vacuum circuit breaker VCB is turned on only for the short time, and the artificial ground fault state appears. . Under this short artificial ground fault condition, the above measurement, the above measurement and data acquisition operation are performed under the control of the microcomputer unit, and subsequently, the above calculation, test signal generation / transmission, response confirmation, and data display. , Such as printing out automatically or keyboard
It is performed according to the command input from.

For example, zero-phase voltage of system-ground fault resistance characteristic and ground fault voltage-
In order to obtain the ground fault current characteristic, _n0 , _n , E before and after the ground fault are measured, and the above equations (1) to (5) are applied. Zero-phase current transformer (ZCT)
To find the characteristics, measure the ground fault current (Ig) and ZCT secondary current (ig) at the time of instantaneous artificial ground fault as described above, and measure the ZCT transformation ratio (Ig).
g / ig) and the primary-secondary phase difference,
It is used as correction data when generating a relay test signal. In the relay test of DG and OVG, the relay input when the ground fault resistance R _g is arbitrarily changed by the above formula and from ₀₀ , ₀₀ ′ obtained by the above ground fault characteristic measurement and the result of the above ZCT characteristic measurement. The voltage and current are calculated and the relay test circuit unit 12 sends the test signal voltage to the relay.
It is applied as a current and the operating value (detection sensitivity) is automatically measured.

All that is required is to open the contact rod 20 and move the contact rod 20 away from the test phase line.

[Effects of the Invention] As described above, the distribution line artificial ground fault test apparatus of the present invention is capable of performing high-speed sampling such as a ground fault device control unit that controls the opening and closing of the ground fault device, zero-phase voltage, and ground fault current. A measurement unit to perform, a simulated zero-phase voltage and a simulated ground fault current as a test signal of the ground fault protection relay, and a relay test circuit unit that measures the operating value of the ground fault protection relay, and controls each of the above units,
Since a predetermined calculation is performed on the output data of the measuring section and the microcomputer section for obtaining the ground fault characteristic of the line which is the basic data for generating the test signal is provided, the artificial ground fault is as follows. It is possible to achieve highly desirable effects for efficiency improvement and safety improvement in the test.

(a) Test transformer (pole transformer) is no longer required,
The device is extremely lightweight, is extremely easy to handle, and requires no countermeasures against ferroresonance.

(b) Since the artificial ground fault time is very short, it is possible to perform the test while the test relay is operating.

(c) Since the equipment is remarkably simplified, the test preparation time and the test time can be greatly shortened, and the number of personnel required for the test can be reduced.

(e) Since all devices can be operated remotely,
The safety of test personnel is ensured.

(f) Since the microcomputer reads the instantaneous data of a plurality of measurement items at a plurality of measurement points with isochronous processing, high measurement accuracy can be secured.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of an artificial ground fault test apparatus of the present invention, FIG. 2 is a connection diagram showing a connection configuration of an example of an artificial ground fault test using this embodiment, and FIG. [Fig. 4] is a connection diagram showing a connection configuration of an example of an artificial ground fault test according to a conventional technique. 1 ... Distribution line artificial fault tester, 2 ... High voltage switching unit, 11 ... Measurement unit, 12 ... Relay test circuit unit, 14 ... Ground fault device control unit, 15 ... Microprocessor, 16 ... Data Memory, 17 ... Program memory.

Claims (1)

[Claims] Claim: What is claimed is: 1. A distribution line artificial ground fault tester for instantaneously artificially grounding a distribution line to measure ground line characteristics and test the operation of a ground fault protection relay: A ground fault device for artificially grounding a distribution line. And a ground fault device control unit that controls switching of the; and a measurement unit that performs high-speed sampling of zero phase voltage, ground fault current, etc .; Generates a simulated zero phase voltage and a simulated ground fault current as a test signal of the ground fault protection relay, A relay test circuit section for measuring the operating value of the ground fault protection relay; a line which serves as basic data for generating the test signal by controlling each of the above sections and performing a predetermined calculation on the output data of the measurement section. 2. A distribution line artificial ground fault test apparatus comprising: a microcomputer section for determining the ground fault characteristic of;