JPS6399716A - Abnormality detecting circuit for instrument transformer - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a voltage transformer for a power circuit, and in particular, when an abnormality such as a short circuit or disconnection occurs on the secondary circuit of a voltage transformer, The present invention relates to an abnormality detection circuit that immediately detects abnormality, prevents malfunction of relays, etc., and issues an alarm.

[Conventional technology]

In conventional devices, a voltage transformer is provided with a main secondary circuit and a sub-secondary circuit, and a power balance relay is installed therein to detect an abnormality in the secondary circuit of the voltage transformer. However, for instrument transformers that do not have sub-secondary circuits, relays cannot be installed and no consideration was given to secondary circuit abnormalities. (Relay Setting Test Manual (
See Denkishoin P34 (4), Voltage Balance Relay))
[Problems to be Solved by the Invention] The above-mentioned prior art is very effective when a voltage transformer is provided with a main secondary circuit and a sub-secondary circuit.
Potential transformers that do not have a sub-secondary circuit are not considered, and there is a problem in that it is not possible to correct a fault in the secondary circuit of a potential transformer with an equivalent circuit.

An object of the present invention is to provide a circuit that can reliably detect abnormalities in the secondary circuit of a voltage transformer even in a voltage transformer that does not have a sub-secondary circuit.

[Means for solving problems]

The purpose of the above is to provide a signal for the voltage transformer protection device that operates when a short circuit or ground occurs in the secondary circuit of the voltage transformer. The zero-sequence current detection relay operates by detecting the zero-sequence current that occurs when a ground fault or disconnection occurs in the power circuit. This is achieved by effectively combining signals.

[Effect]

Potential transformer protection devices act immediately when a two or three wire short circuit or a -wire ground fault occurs in the secondary circuit of a potential transformer. The output signal of the protection device immediately prevents the operation of the protection relay or control device connected as a load of the potential transformer, and also provides an alarm. The zero-sequence voltage detection relay operates by detecting the zero-sequence voltage that occurs due to a ground fault or disconnection accident on the secondary circuit of a voltage transformer. However, since the zero-sequence voltage detection relay also detects zero-sequence voltage caused by a ground fault or disconnection accident on the power circuit via the voltage transformer, Operate. The zero-phase current detection relay is used to detect ground faults on the power circuit, or
It operates by detecting zero-sequence current caused by a disconnection accident. The zero-sequence current detection relay does not operate even if a ground fault or disconnection occurs on the secondary circuit of the voltage transformer because zero-sequence current does not flow in the power circuit. A ground fault or disconnection fault can be detected by combining the operating signal of the zero-sequence voltage detection relay and the non-operation signal of the zero-sequence current detection relay. #If a ground fault or disconnection fault in the secondary circuit of a voltage transformer is detected by the combination of the phase voltage detection relay and zero-phase current detection relay, the detection signal will be the output signal of the voltage transformer protection device. Similarly, it immediately prevents the operation of protection relays and control equipment connected as loads of potential transformers. At this time, a warning is output after a certain period of time. This is to prevent alarm output if a ground fault or short circuit without zero-sequence current occurs on the power circuit until the fault is removed by the protection device.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In the figure, power circuits 1, 2, 3. Potential transformers 4, 5, 6 connected to The first winding on the input side and the second winding on the output side are each connected in a star shape. The output of the second winding is connected to the potential transformer protector 7 and the cables 8.9, 10, 11. through the zero-phase voltage detection relay 12 and the power circuit protection relay 1
Connected to 3.

Also, power circuits 1, 2, 3 . Instrument current transformer 14゜I Eit with the first winding connected to and the second winding connected in a star shape
16 +, one of the second windings is connected to one terminal of the zero-phase current detection relay 17 through each power circuit protection relay 13, and the other side (neutral phase) of the second winding is connected directly to one terminal of the zero-phase current detection relay 17. It is connected to the other terminal of the zero-phase current detection relay 17.

Operation signal 18 of voltage transformer protection device 7. Operation signal 19 of zero-phase voltage detection relay 12, zero-phase current detection relays 1 and 7
NOT circuits 21, 26, . AND circuits 22, 27. Timed relay 23. OR circuits 24, 25 are provided.

The output signal 30 of the AND circuit 27 is used for tripping control of the circuit breaker, and the output multiple 29 of the OR circuit 24 is connected to a failure alarm circuit to display and alarm an abnormality in the secondary circuit of the voltage transformer.

When a short circuit accident F1 occurs between cables 8 and 9, which are the secondary circuit of the voltage transformer 4, if the short circuit occurs at the point F1, the voltage transformers 4, 5, . Cable 8.9 short-circuit point Fl,
And instrument transformer protection bag ff! A short-circuit current flows through 7, and the voltage transformer protection device 7 operates. When the voltage transformer protection device 7 operates, the operation signal 18 is sent to the OR circuit 2.
given to 4. When a signal is given to the OR circuit 24, O
The output signal 29 of the R circuit 24 is given to a failure alarm circuit,
Displays and alarms abnormalities in the secondary circuit of the instrument transformer. At this time, an abnormal voltage is supplied to the power circuit protection relay 13 due to a short circuit accident at the F1 point, and the power circuit protection relay 13 malfunctions. 1! Operation signal 2 is generated by the operation of power circuit protection relay 13.
8 is applied to the A N D circuit 27 . However, AND
No signal is applied to the other side of the circuit 27 because of the operating signal 18 of the potential transformer protection device 7. Therefore, the AND circuit 27 is not established and the output signal 3o is not output. This does not cause any problems.

When a disconnection accident F2 occurs in the cable 8, which is the secondary circuit of the instrument transformer 4, when the disconnection accident F2 occurs at the point F2, a zero-sequence voltage is generated in the secondary circuits of the instrument transformers 5 and 6. Zero-phase voltage detection relay 12 operates, and output signal 19 is applied to one side of AND circuit 22 . Also, at this time, the power circuit 1,
2.3 Since there is no ground fault, the zero-sequence current does not flow to the power circuit and the zero-sequence current detection relay 17 continues to be inoperative, and the operation signal 20 is not output. This means that the operating signal is not continuously applied. Since no signal is applied to the NOT circuit 21, the NOT circuit 21 outputs a signal. AND22 outputs a signal when a condition is met by the output signal 19 and the signal from the NOT circuit 21. The signal output from the AND 22 is applied to the OR circuit 24 after a certain period of time by the time limit relay 23. When a signal is given to the OR circuit 24, the OR circuit 24
The output signal 29 of circuit 24 is provided to a fault alarm circuit to indicate and report an abnormality in the voltage transformer secondary circuit. At this time, F
Due to the two-point disconnection accident, abnormal voltage is supplied to power protection relay -13, power circuit protection relay 13 malfunctions, and operation signal 28 is given to AND circuit 27.

However, no signal is given to the other side of the AND circuit 27 due to the operation of the zero-phase voltage detection relay 12, so
The circuit is not established and the output signal 30 is not output, which does not cause any problem.

A case where a ground fault occurs in the power circuit 1 is shown.

When a ground fault F3 occurs in the power circuit, the zero-phase current detection relay 17 operates and outputs an output signal 20. At this time, the zero-phase voltage detection relay 12 also detects the zero-phase voltage caused by a ground fault in the power circuit via the instrument transformers 4, 5.6, operates, and outputs an output signal 19.

At this time, the AND circuit 22 does not output a signal because the operation signal 20 of the electric phase current detection relay 17 is not satisfied, and at this time, of course, the instrument protection device 7 also does not operate, and the operation signal 18 is also output. has not been done, therefore, OR
The circuit 24 is not established, and the output signal 27 is not output.Therefore, there is no indication or alarm of an abnormality in the secondary circuit of the instrument transformer.In addition, the power circuit protection relay 13 is activated due to the ground fault F3, and the output signal 27 is not output. A signal 28 is output. At this time,
Since there is no output signal from the AND path 22 and also because there is no output signal 18 from the potential transformer protection device 7, there is no output signal from the OR circuit 25, so the AND 27 is established. AND
When the output signal 30 is output from 27, the breaker can be tripped. This does not cause any problems.

〔Effect of the invention〕

According to the present invention, it is possible to detect an abnormality in the secondary circuit of a voltage transformer without affecting the power circuit protection relay, etc., even in a circuit where the voltage transformer does not have a sub-secondary circuit. .

[Brief explanation of the drawing]

The figure is a circuit diagram for detecting an abnormality in the secondary of a voltage transformer according to an embodiment of the present invention.

Claims (1)

[Claims] 1. In a circuit comprising a three-phase power circuit, a voltage transformer for converting the voltage of the three-phase power circuit, and a voltage current transformer for converting the current, two of the voltage transformers are An instrument transformer, characterized in that the next circuit is equipped with a protection device for the instrument transformer and a zero-phase voltage detection relay, and a neutral phase of the instrument current transformer is equipped with a zero-phase current detection relay. abnormality detection circuit.