JPH02105073A - Artificial ground-fault testing device for distribution line - Google Patents

Abstract

PURPOSE:To make the device light in weight by providing a ground-fault control part for executing an opening/closing control of a ground-fault device, a relay testing circuit part for measuring an operation of a ground-fault protective relay, and a microcomputer part for deriving a ground-fault characteristic of a line. CONSTITUTION:When a test start push-button of an artificial ground-fault testing device 1 is pushed, a turn-on signal of a short time is sent out to a vacuum circuit breaker of a high voltage opening/closing part from a microcomputer part (a CPU 15, a data memory 16, a program memory 17) and only during that time, the vacuum circuit breaker is turned on, and an artificial ground-faul state appears. Under this artificial ground-fault state, a phase voltage, a ground-fault current, a zero-phase current, a zero-phase voltage and their phase angles are measured, and also, by an operation of the microcomputer part, a parameter of a distribution line is derived. Also, at the time of a relay test, a voltage and a current of a relay input are derived by an operation in the microcomputer part, applied as a voltage and a current of a test signal to a relay from a relay testing circuit part 12 and an operation value is measured automatically. In such a way, a test use transformer becomes unnecessary, and the device is made light is weight.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a distribution line artificial ground fault testing device that instantaneously causes a ground fault in a distribution line, measures the line-to-ground line characteristics, and tests the operation of a ground fault protection relay. It is something.

[Conventional technology]

Conventionally, when a ground fault occurs in a distribution line, various types of ground fault protection relays (hereinafter simply referred to as relays) are used to cut off the faulty line and separate it from the healthy circuit.
The magnitude of the zero-sequence voltage and ground fault current that occur in the event of a ground fault differs for each system depending on the line characteristics determined by the line length, etc., so relay setting, that is, the setting of the relay operating value, should be adjusted to suit the characteristics of each line. It is necessary to do so.

However, the ground admittance i required for relay setting
It is extremely difficult to obtain accurately by calculation1.
Therefore, the current method is to artificially create a ground fault on the line and determine the operating value of the relay based on the ground fault line characteristics obtained through actual measurements. Generally, each distribution line is artificially grounded through a test transformer (distribution transformer 6.6 kV), and a water resistor connected to the secondary side of the test transformer is adjusted to reduce the ground fault current. By actually measuring the ground fault resistance-ground fault voltage and ground fault voltage-ground fault current characteristics at several points while adjusting and subtracting, the line characteristics are obtained, and the operating value of the relay is determined based on the characteristics.

An example of a test circuit used in such an artificial ground fault test is shown in FIG. The illustrated test circuit is configured to measure the line characteristics of the distribution line connected to the 6kV bus of the distribution system via circuit breaker CB and disconnectors DSa and DSb. Use a switching busbar. Based on the measurement results, the operating points (sensitivity) of the ground fault direction relay DG and the ground fault overvoltage relay 0G for operating the circuit breaker CB are set. Reference numeral 30 in the figure is a connecting rod, 3
1 is a water resistor, 32 is a test transformer (ball transformer)
, 33 is a suppression resistor for preventing iron resonance, AS (OS) is a high-voltage switch, FDS is a disconnector with a fuse, Vo is a voltmeter for measuring zero-phase voltage, ph is a phase meter, and Vg is a voltage for measuring ground fault voltage. Ig is an ammeter for measuring ground fault current, and GPT is a grounding type potential transformer. To explain the measurement operation, first, circuit breaker CB, disconnectors DSa and DSb are closed, and the distribution line is in the power transmission state. It has become. In addition, disconnectors DSc, D
Si and high voltage switch AS are open, disconnector with fuse FD
S is put in, and one electrode plate of the water resistor 31 is taken out from the water (maximum resistance value). In this state, the test rod 30 is brought into contact with the phase line to be tested (T phase in the illustrated case) of the switching bus bar, and the disconnector DSc(t) of that phase is turned on.

Next, the high voltage switch AS is turned on to generate an artificial ground fault, and the DSi is turned on to bypass the suppression resistor 33, and in this state, the water resistance is adjusted (the resistance value is gradually decreased from the maximum value). Vg, including the operating points of the ground fault directional relay DG and the ground fault overvoltage relay OVG.

Measure and record the indicated values of Vo, Ig, and Ph at several points.

[Problem to be solved by the invention]

However, the conventional artificial ground fault test described above has the following problems, and there has been a demand in the electric power industry and the like for the development of a device that solves these problems.

■ The test equipment is heavy, and the circuitry at the measurement site is complicated, making it extremely difficult to handle.

■ Because delicate adjustments to the water resistor are required, the time during which the ground fault current flows is relatively long, and the protection reliability decreases because the ground fault protection relay cannot be used during that time.

■ Measures are required to prevent abnormal voltages caused by iron resonance in test transformers.

More specifically, the above method of creating an artificial ground fault using a ball transformer or water resistance and measuring the line characteristics of the distribution line and the operating point of the DG relay with a voltmeter and ammeter requires a very heavy ball transformer. In addition, since the ground fault resistance is variably adjusted by water resistance, the constantly fluctuating voltage and current must be measured visually, which requires a large amount of time for preparation and measurement. Additionally, there is a risk of abnormal voltage generation due to abnormal resonance, which is estimated to be caused by the inductance of the transformer and the ground capacity of the distribution line.

This invention was made in view of the above circumstances, and its purpose is to provide an arrangement that does not require a test transformer, is lightweight, and can easily and quickly perform an artificial ground fault test with a simplified device configuration. By providing a wire artificial ground fault testing device, the purpose is to semi-automate artificial ground fault testing, reduce the amount of work, shorten testing time, and promote danger prevention.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a distribution line artificial ground fault testing device that instantaneously causes an artificial ground fault in a distribution line to measure the line-to-ground line characteristics and test the operation of a ground fault protection relay: opening and closing of a ground fault device; A ground fault device control section that performs control; a measurement section that performs high-speed sampling of zero-sequence voltage, ground fault current, etc.; A relay test circuit section that measures the operating value of the protective relay; controls each of the above sections, performs predetermined calculations on the output data of the measurement section, and tests the track ground, which is the basic data for generating the test signal. It is equipped with a microcomputer section for determining the contact characteristics;

[Effect]

Line constants of distribution systems where the neutral point is ungrounded, that is, three-phase −
Boundary equilibrium admittance? . . and three-phase-discharge equilibrium admittance? . . ' is the following formula, assuming the ground fault resistance value as R1.
and ■ are given. Also, zero-sequence voltage ♀ when one wire is grounded.

and ground fault current! are given by the following formulas ■ and ■, respectively.

? . .・=-zuj 工■-66816909,1140,
(1) 0,■+=E+λ−・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・■R.

However, Emperor. : Residual zero-sequence voltage during non-ground fault,
: Zero-sequence voltage E when a ground fault occurs with an arbitrary resistor (R5): To the phase voltage 2 Coefficients that vary depending on the ground fault phase: R phase ground 1, Q person due to fault = 1. S-phase ground fault = 2'2'tv'T T-phase ground fault = -T+'' In other words, residual zero-sequence voltage in the system at all times! ,. Then, any phase is grounded with a grounding resistance R, and the zero-sequence voltage t at that time is measured.
By measuring , the line constant can be determined. The distribution line artificial ground fault test device of the present invention having the above configuration performs a short-time artificial ground fault using the fixed resistor of the ground fault device, and calculates the ground fault characteristics of the system from the data obtained as a result. Furthermore, this characteristic is used to test the operation of the relay.

More specifically, under the control of a microcomputer, a ground fault device control section instantaneously closes the ground fault device to cause an artificial ground fault on the line, and a measurement section measures the zero-sequence voltage, ground fault current, etc. at the time of the ground fault. sample at high speed. The microcomputer section inputs the data obtained through this sampling and calculates the ground fault characteristics of the line by performing calculations based on the above equations 0 and 0, and also calculates the ground fault characteristics obtained in this way. Based on this, the relay test circuit section supplies a simulated zero-sequence voltage and a simulated earth fault current to the earth fault protection relay,
Based on the response, the operating value of the ground fault protection relay is measured.

The artificial ground fault test device of the present invention can perform measurement, data recording, calculation, and other processing instantly as described above, so that artificial ground faults can be replaced with heavy ball transformers and water resistance by pure resistance components. This can be done with fixed resistors.

〔Example〕

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

In the distribution line artificial ground fault test device 1 of the embodiment shown in FIG. It consists of n sample and hold (S/H) circuits ILL (1=1 to nχ multiplexer 114 and analog-to-digital (^/D) converter 115, each connected to the relay test circuit 12. Input/output switch 121, voltage amplifier 122, amplitude adjuster 123, phase adjuster 124, digital input/output device 1
25, consists of a sine wave generator t2a, an amplitude adjuster 127, and a current amplifier 128, and the microcomputer section is a microprocessor (CPU) 15, data memory 16
and a program memory 17.

This device further includes a ground fault device control section 14 consisting of a digital input/output device 141 and a relay driver 142, and an interface (1/F) device 1131. Printer 13
2. Liquid crystal display (LCD) 133 and keyboard 13
A data input/output section 13 consisting of 4 and a power supply device 18 are provided. The artificial ground fault test device of this embodiment has contact rod 2.
Used with high voltage switchgear (earth fault device) 2 having 0,
High voltage switching section 2 is a 7.2kV vacuum circuit breaker VCB, 8Ω
It consists of a ground fault fixed resistor RO1, a current transformer CTO, a protective power fuse PF, etc.

Line voltage and ground voltage are input to the input converter 111 of the measuring section 11 from the secondary side is input. Note that the filter 112 and the sample and hold (S/) circuit 113. The reason why multiple (n) series circuits are installed in parallel is to simultaneously sample multiple measurement elements such as three-phase voltage, zero-phase voltage, and ground fault current at different measurement points. This is to enable the A/D converter 115 to convert the data into digital data. In addition, the input/output switch 121 of the relay test circuit section 12 receives a zero-sequence voltage Vo from the tertiary side Y of the grounded potential transformer GPT, and a secondary current ig from the secondary side of the zero-phase current transformer ZCT. A contact operation signal is input to the digital input/output device 125 from the ground fault direction relay DG or the ground fault overvoltage relay OvG.

Measurements including voltage, current, and phase angle are performed at high speed under the control of a microcomputer unit (CPuts, Data Memo January 6, Program Memo 1J17).

Therefore, the time required for a ground fault due to the pure resistance (fixed resistor RO) of the high voltage switching section 2 is extremely short, about 0.5 seconds. Artificial ground fault due to pure resistance of high voltage switching section 2 causes phase voltage, ground fault current,
The zero-sequence current, the zero-sequence voltage, and the phase angle between these are measured, and the parameters (admittance, etc.) of the distribution line are calculated by the microcomputer based on these measurement data. The distribution line characteristics are calculated by admittance calculation using the parameters obtained in this way.

Furthermore, based on the calculation results, the ground fault current, zero-sequence current, zero-sequence voltage, and phase angle between them at any ground fault resistance are determined.

Then, by calculating the continuous zero-sequence current, zero-sequence voltage, and phase angle between them, assuming that the ground fault resistance is gradually lowered from a high resistance value, the actual zero-sequence current,
A test signal corresponding to the zero-sequence voltage is generated by the relay test circuit section 12 under the control of the microcomputer section,
In addition to the DG relay or OvG relay being tested, check the operating point or response operation of these relays. Therefore, it is not necessary to conduct a test to confirm relay operation by actually gradually changing the ground fault resistance in the artificial ground fault test.

In addition, in the parameter measurement of the above-mentioned distribution line, the ground fault current, zero-sequence current, zero-sequence voltage, phase angle between these, admittance, etc. are displayed on the LCD 133 of the data input/output unit 13.
These data can be displayed on the screen of the printer 132, and can be printed out using the printer 132. In addition, in OG and OvG relay tests, data on the relay operating point is displayed and printed out.

Next, an example of measurement and test operations using the artificial ground fault testing device of this embodiment will be briefly explained with reference to FIG.

First, the circuit breaker CB, the disconnectors DSa, and DSb are in the closed position, and the distribution line is in a power transmission state, and the circuit breaker DSc is open and the switching bus is in a non-power transmission state. In addition, the high voltage opening/closing part 2
Vacuum circuit breaker VCB is open. To conduct the test, the grounding rod 20 connected to the high-voltage switching unit 2 is brought into contact with the phase line to be tested (T phase in the illustrated case) of the switching bus, and the disconnector DSc(t) of that phase is turned on.

In this state, press the test start button (
(not shown) is pressed, the digital input/output device 14 of the ground fault device control section 14 is pressed under the control of the microcomputer section.
1 and the high voltage switching section 2 via the relay driver circuit 142.
A short-time closing signal is sent to the vacuum circuit breaker VCH, and the vacuum circuit breaker VCB is closed for only that short period of time, thereby creating an artificial ground fault condition. Under this short artificial ground fault condition, the above measurements and data acquisition operations are performed under the control of the microcomputer section, followed by the above calculations, test signal generation/sending, response confirmation, and data display. ,
Operations such as printing out are also performed automatically or in response to command input from the keyboard 134.

For example, the zero-sequence voltage of the system - ground fault resistance characteristics and ground fault voltage -
9 before and after the ground fault to determine the ground fault current characteristics. ,? ,,
Measure E and apply equations ① to ① above. Zero-phase current transformer (
To determine the ZCT) characteristics, measure the ground fault current (Ig) and ZCT secondary current (1g) when an instantaneous artificial ground fault occurs as described above, and calculate the ZCT transformation ratio (Ig/ig) and -order primary The phase difference is determined and used as correction data when generating test signals for DC relays and OVG relays. Also, DG,
In the OVG relay test, the ? ,. ,? . . ′ and from the results of the above ZCT characteristic measurement, calculate the relay input terminal current when arbitrarily changing the ground fault resistance R, using the above formulas ① and ②,
A test signal voltage and current are applied to the relay from the relay test circuit section 12 to automatically measure the operating value (detection sensitivity).

After the above measurement and data acquisition, it is sufficient to simply open the disconnector DSc(t) and separate the contact rod 20 from the phase line under test.

〔Effect of the invention〕

As explained above, the distribution line artificial ground fault testing device of the present invention includes a ground fault device control section that controls opening and closing of the ground fault device, a measurement section that performs high-speed sampling of zero-sequence voltage, ground fault current, etc. A relay test circuit section that generates a simulated zero-sequence voltage and a simulated ground fault current as a test signal for the ground fault protection relay, and measures the operating value of the ground fault protection relay, and controls each of the above sections and output data of the measurement section. The structure is equipped with a microcomputer section that performs predetermined calculations on the ground fault characteristics of the line and obtains the ground fault characteristics of the line, which is the basic data for generating the test signal.As described below, it improves efficiency and safety in artificial ground fault tests. It is possible to achieve extremely desirable effects such as improving sexual performance.

(a) Test transformer (ball transformer) is no longer required,
The device is significantly lighter in weight, extremely easy to handle, and does not require any fero-resonance countermeasures.

(bl) Since the artificial ground fault time is very short, the test can be performed while the relay under test is in operation.

fc) Since the equipment is significantly simplified, the test preparation time and test time are significantly shortened, and the number of personnel required for the test can also be reduced.

All tel equipment can be operated remotely, ensuring the safety of test personnel.

g) Since the microcomputer reads and processes the instantaneous data of a plurality of measurement items at a plurality of measurement points in an isochronous manner, high measurement accuracy can be ensured.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the artificial ground fault testing device of the present invention, FIG. 2 is a wiring diagram showing the connection configuration of an example of an artificial ground fault test using this embodiment, and FIG. 3 1 is a wiring diagram showing a connection configuration of an example of an artificial ground fault test according to the prior art. l......Distribution line artificial ground fault test equipment, 2...
・・・・・・High voltage opening/closing part, 11・・・・・・
... Measuring section, 12... Relay test circuit section, 14... Earth fault device control section, 15...
・・・・・・Microprocessor, 16・・・・・・・
...Data memory, 17.--.--.Program memory.

Claims (1)

[Claims] (1) In a distribution line artificial ground fault testing device that momentarily causes an artificial ground fault in a distribution line to measure the line-to-ground line characteristics and test the operation of a ground fault protection relay: Opening and closing of a ground fault device that causes an artificial ground fault in a distribution line A ground fault device control section that performs control; A measurement section that performs high-speed sampling of zero-sequence voltage, ground fault current, etc.; A relay test circuit section that measures the operating value of the protective relay; controls each of the above sections, performs predetermined calculations on the output data of the measurement section, and tests the track ground, which is the basic data for generating the test signal. A distribution line artificial ground fault testing device comprising: a microcomputer section for determining fault characteristics;