JPS61109416A - Ground protective relay device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a digital earth fault protection relay device applied to a high resistance grounding system.

[Technical background of the invention and ranking points]

In a power transmission system with a high resistance grounding system, a power transmission line is installed at an electric station. A breaker is connected to the terminal of this power transmission line, and a zero-sequence voltage is applied to each ground fault appropriate voltage relay via the tertiary winding l1I (broken delta connection) of the potential transformer.

Next, when a ground fault occurs on the grid side, a zero-sequence voltage is generated in the tertiary winding of the instrument transformer, and this zero-sequence voltage becomes the input electricity to the ground fault overvoltage relay, generating a voltage higher than the set value. Then, a trip signal is given to the breaker to eliminate the fault.

In a ground fault protection relay device based on the above principle, if we consider a one-wire ground fault on the secondary side of a voltage transformer, a broken delta connection of the voltage transformer is considered even though there is no fault on the grid side. A zero-sequence voltage is generated in the tertiary circuit.

The setting value of the ground fault overvoltage relay is usually 30 for this zero-sequence voltage.
% ground fault is the detection target.

In the case of a one-wire ground fault or disconnection mode of a capacitor type transformer, connect the voltage transformer to the tertiary circuit of the voltage transformer on the secondary side.
A voltage of about V/3 is generated, resulting in a trip command being given to the disconnector. Father, if the same 1m protection capability is added to other power transmission line protection devices, all lines connected to the electrical station may be cut off, causing a supply failure.

For this reason, in conventional earth fault protection relay devices, the setting value of earth fault overvoltage relays, etc. is set to 110V/3 or higher, and measures are taken to prevent unnecessary interruption due to an accident on the secondary side of a voltage transformer. We are trying to

In this way, it is possible to prevent unnecessary tripping due to a fault on the secondary side of a voltage transformer by coordinating the settings of ground fault overvoltage relays, but the current situation is that the relay's inherent sensitivity decreases. be.

[Purpose of the invention]

The present invention was made for the purpose of solving the above-mentioned problems, and by digitalizing it, it is possible to calculate whether it is a system fault or a fault on the secondary side of a voltage transformer without adding a 1-F. The purpose of the present invention is to provide a digital ground fault protection relay device that can detect system faults with high sensitivity without reducing sensitivity.

[Summary of the invention]

The present invention focuses on the fact that the zero-sequence voltage is larger than the negative-sequence voltage in the case of a one-wire ground fault in the system, and if this ratio is greater than a certain constant, it is determined that the fault is on the secondary side of the voltage transformer. This is a ground fault protection relay device that makes a judgment in the arithmetic circuit of the ground fault protection relay device and prevents unnecessary tripping of the circuit breaker in the event of a potential transformer accident.

That is, the present invention uses a ground fault protection relay device for a high resistance grounding system to determine whether a ground fault occurs on the grid side or on the secondary side of a voltage transformer by determining the ratio of zero-sequence voltage to negative-sequence voltage. This is a ground fault protection relay device that is identified by the presence of a certain value or more, and has a locking function so that the protection relay device does not operate unnecessarily in the event of an accident on the secondary side of a voltage transformer. .

[Embodiments of the invention]

Next, examples of the present invention will be described. Figure 1' shows the input converter 21 that introduces the voltage value 13A applied to the protected power transmission line 11 and the voltage value 1 introduced to the input converter 21.
A filter 22 that passes only the input necessary for digitization out of 3A, a multiplexer n that extracts the instantaneous value data of the output of the filter 22 in time series in synchronization with the sampling frequency, and a digital output signal 23A of the multiplexer Yu. a conversion unit 24 that converts into a signal 24A; an arithmetic processing unit 25 that receives the digital signal 24A from the conversion unit 24 and determines whether the protected power transmission line 11 has a ground fault;
Breaker tripping signal 18 output from the arithmetic processing unit 25
A digital ground fault protection relay device is shown.

The calculation flowchart in FIG. 2 corresponds to the calculation processing section 25 in FIG. It is. First, when an accident occurs, in step 31 it is determined whether it is a fault on the grid side or a fault on the secondary side of the voltage transformer a (V
m + a ”Vk +aVa )/a(Va +
Vb+Vs) k is judged, and if it is less than a certain constant, it is judged as a system fault. va *Vb, v is each phase voltage,
a, a music vector operator. In addition, at the step, it is determined whether the zero-sequence voltage V in the case of a ground fault in the system is above or below the set value (Vset) of the relay, and if it is above the set value, it is determined that the ground fault overvoltage relay is activated, and it is not activated. If so, proceed to step 35.

Further, the operation of the fail-safe element is checked in step 32. If the fail-safe element is working, the process proceeds to step 33, and if it is not operating, the process proceeds to step 35. Once you get to step 33,
In step 34, a tripping command is given to the breaker on the condition that the operation continues for several cycles.

Here, the constants in step 31 include negative phase and zero phase voltages that occur due to unbalanced load current, etc., and impedance 5.
This is a value determined by taking into account 5th grade.

〔Effect of the invention〕

In this way, the arithmetic processing unit can determine whether or not the fault is on the grid side, and prevent the ground fault overvoltage relay from operating unnecessarily in cases other than grid faults. It is possible to provide a simple device that can detect electrical faults and does not require additional hardware.

According to the present invention, a digital ground fault protection relay has a judgment function to detect and eliminate faults with a sensitivity of 17.1 to 11 in case of ground faults on power transmission lines where the low sensitivity of the ground fault protection relay cannot be tolerated. equipment can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a ground fault protection relay device showing an embodiment of the present invention, and FIG. 2 is a block diagram showing the calculation process of the ground fault overcurrent (E9 relay) shown in FIG. 21...Input converter, 22...Filter 23...
・Multiplexer, 24...Conversion unit 25...Arithmetic processing unit Agent Patent attorney Noriyuki Kensuke Chika (one idiot) rtX Figure 1 Figure 2

Claims (1)

[Claims] An input converter that inputs the AC voltage of the power system transformed by the instrument transformer, a filter that passes only the information necessary for digitization from the output voltage converted by this input converter, and the output of this filter. a multiplexer that extracts the instantaneous value data in time series in synchronization with the sampling frequency; a conversion unit that converts the analog output signal from the multiplexer into a digital signal;
The digital signal from this converter is input, and based on the ratio of the negative sequence voltage and the zero sequence voltage, it is determined whether it is a ground fault in the power system or a fault in the instrument transformer, and based on this determination result, a breaker trip signal is generated. An earth fault protection relay device comprising: an arithmetic processing unit that outputs