JP2970728B2 - Ground fault directional relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault directional relay capable of performing an automatic characteristic test.

[0002]

2. Description of the Related Art A conventional ground fault directional relay having a structure shown by a symbol 1 'in FIG. 3 is used. In this case, the zero-phase voltage V0 and the zero-phase current I0 are supplied to an arithmetic circuit 20 via a BPF (bandpass filter) 2. The arithmetic circuit 20 alternately takes in the zero-phase voltage V0 and the zero-phase current I0, samples and holds the sample-and-hold circuit 6, an A / D converter 7 that converts the output signal of the sample-and-hold circuit 6 into a digital signal, and the zero-phase voltage V0. And a phase difference detection circuit 12 for detecting a phase difference between the zero-phase current I0 and the output signal of the A / D converter 7 so as to drive the operation output contact 9 when a ground fault is detected by the CPU 8. Has become. The CPU 8 calculates the effective value of the zero-phase current and the zero-phase voltage from the time-sharing input waveform data,
A signal from the phase difference detection circuit 12 is input, a ground fault is determined from the values of the zero-phase current and the zero-phase voltage, and the operation output contact 9 is operated. During the test, an operation test is performed by supplying a signal obtained by superimposing the test zero-phase current and the test zero-phase voltage from the auxiliary transformer 15 via the test switch 16 to the arithmetic circuit 20. In this case, the test signal to be superimposed is a signal in which the test zero-phase voltage and the zero-phase current are in phase and sufficiently larger than the set value at which the arithmetic circuit 20 detects a ground fault.

FIG. 4 shows the configuration of a main circuit in which a ground fault directional relay 1 'constructed as described above is used. In the figure, reference numeral 22 denotes a main circuit for supplying power to a load, and reference numeral 20 denotes a circuit breaker for dividing the main circuit 22. Reference numeral 21 denotes a zero-phase voltage detecting device for detecting a ground fault voltage generated when a ground fault occurs in the main circuit 22.
Is a zero-phase current transformer for detecting a ground fault current. When a ground fault occurs, the device configured as described above has a zero-phase voltage V
0 and zero-phase current I0 are generated and input to the ground fault direction relay 1 'by the respective detection devices. The ground fault direction relay 1 ′ determines the magnitude of the input zero-phase current and zero-phase voltage and determines the phase characteristic, and determines that a ground fault has occurred in the main circuit 22. Sends a cutoff signal. Therefore, even if a ground fault occurs in any of the loads A and B or the power supply, the portion where the ground fault has occurred can be separated from the main circuit 22.

[0004]

However, in such a conventional apparatus, it is necessary to cause a power failure of a main circuit when performing an operation test, and when further performing an operation test, the main circuit is powered down and a ground fault relay is required. There is a problem that it is necessary to input a zero-phase voltage and a zero-phase current from an external test power supply to the removed ground fault relay. In particular, a ground fault relay is required to perform a characteristic test at intervals of about once a year, and it is necessary to cause a power failure each time. The present invention has been made in view of such a situation,
The purpose of the test is to perform a test without stopping the main circuit and without removing the ground fault relay.

[0005]

In order to solve such a problem, a ground fault directional relay according to the present invention generates a test signal.
Test signal generation circuit to compare test signal with zero-phase voltage
And select the signal with the larger amplitude,
A first analog OR circuit for outputting only the test signal
Compare with the phase voltage, select the signal with the larger amplitude,
A first analog AND circuit that outputs only the negative signal
And the test signal and the zero-sequence current.
A second signal for selecting a signal and outputting only its positive signal
Compare the analog or circuit with the test signal and the zero-phase current, and
Select the signal with the larger width and output only the negative signal.
A second analog AND circuit, and a first analog
Circuit output signal and first analog AND circuit output signal
A first addition circuit for adding a signal, and a second analog or
Circuit output signal and the second analog AND circuit output signal.
Second adding circuit for adding, and first and second adding circuits
Operation to judge at the time of test and detect ground fault accident from output
And a circuit. This place
In this case, one configuration example of the above-described ground fault directional relay is an arithmetic circuit.
Activated by ground fault detection and outputs a shutoff signal to the circuit breaker
The operation output contact that is generated and only the test signal
Is activated when the power is
And an operation lock contact for inhibiting.

[0006]

In the device constructed as described above, the test signal generated by the CPU control and the zero-phase voltage and the zero-phase current from the main circuit are superimposed by the analog OR circuit and the analog AND circuit, and are calculated by the arithmetic circuit. Perform tests and determine abnormalities.

[0007]

FIG. 1 is a block diagram showing an embodiment of the present invention, and the same parts as those in FIG. 3 are denoted by the same reference numerals and their description is omitted. 3a and 3b receive an actual input signal and a test signal, of which a signal having a larger amplitude is selected,
This is an analog OR circuit that outputs only the positive signal . 4a and 4b receive an actual input signal and a test signal, of which the input signal having the larger amplitude is selected.
An analog AND circuit that outputs only the negative signal ,
a is an addition circuit that adds the output signals of the analog OR circuit 3a and the analog AND circuit 4a; and 5b is an addition circuit that adds the output signals of the analog OR circuit 3b and the analog AND circuit 4b. The CPU 8 in the arithmetic circuit 20 has a function of taking in a signal from the operation detection circuit 11 that has detected the operation of the operation output contact 9 and outputting a test signal to the D / A converter 13 in addition to the function in FIG. Has been added. 14 is D /
LPF for shaping the output signal waveform of A converter 13
(Low-pass filter).

In the device configured as described above, a zero-phase voltage V0 from a zero-phase voltage detector (not shown) is supplied to the analog OR circuit 3a and the analog AND circuit 4a via the band-pass filter 2. Similarly, a zero-phase current I0 from a zero-phase current transformer (not shown) is supplied to the analog OR circuit 3b and the analog AND circuit 4b via the band-pass filter 2.

FIG. 2 shows the analog OR circuit 3a and the analog AND circuit 4a as representatives, and explains the operation. These circuits generate an AC signal as shown in FIG. By being input, the output of the analog OR circuit 3a has a waveform higher than 0V as shown in the figure. Analog and circuit 4
As for the output of a, a portion having a potential lower than 0 V is output as shown in FIG. When these signals are added by the adding circuit 5,
The input waveform is restored and output.

That is, when the test signal is 0, a signal corresponding to a zero-phase voltage and a zero-phase current, which are actual input signals, is output. When no accident occurs, the zero-phase current and the zero-phase voltage are zero, so that a signal is output when a test input is supplied.

Since the test input signal is controlled by the CPU 8, the test input corresponding to the zero-sequence voltage and the zero-sequence current can be arbitrarily controlled by the CPU 8 for both the potential and the phase difference. It can be carried out. Further, since the operation lock contact 10 is provided, if the contact is locked during the test input superimposition, the cutoff signal is not output, and if the operation of the operation output contact 9 is detected by the operation detection circuit 11, It becomes possible to automatically perform a test of the directional relay.

Further, the signal which will be read from the adding circuit 5 if an accident occurs is different from the signal which CPU 8 is generated because during the test, CPU 8 can know the occurrence of an accident by comparing it. In this case, the test can be interrupted and the protection operation can be started, so that safety is ensured even during the test.

[0013]

As described above, according to the present invention, the test input and the actual input are combined by the analog OR circuit and the analog AND circuit, and then added, and the addition result is monitored by the CPU. This has the effect that an online automatic test can be performed without removing the ground fault directional relay.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating operations of an analog OR circuit and an analog AND circuit.

FIG. 3 is a block diagram illustrating a configuration of an example of a conventional device.

FIG. 4 is a block diagram showing a configuration of a ground fault direction relay.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ground fault direction relay main body 2 BPF (Band pass filter) 3 Analog OR circuit 4 Analog AND circuit 5 Addition circuit 6 Sample hold circuit 7 A / D converter 8 CPU 9 Operation output contact 10 Operation lock contact 11 Operation detection circuit 12th Phase difference detection circuit 13 D / A converter 14 LPF (low-pass filter)

Claims (2)

(57) [Claims] 1. A ground fault based on a zero-phase current and a zero-phase voltage
In a ground fault directional relay for detecting a test signal, a test signal generating circuit for generating a test signal, the test signal and the zero-phase voltage are compared,
1) that selects one of the signals and outputs only its positive signal
And the test signal and the zero-sequence voltage are compared with each other.
1) that selects one of the signals and outputs only its negative signal
And the test signal and the zero-phase current are compared with each other.
Second signal which selects one of the signals and outputs only its positive signal
And comparing the test signal and the zero-phase current, the amplitude of which is large.
Second signal which selects one of the signals and outputs only its negative signal
Analog AND circuit, the first analog OR circuit output signal and the first
A first adding circuit for adding an analog AND circuit output signal
If the second analog OR circuit output signal and the second
Second adder circuit for adding analog and circuit output signal
From the outputs of the first and second adder circuits,
And an arithmetic circuit for detecting ground faults.
Ground fault directional relay. 2. The circuit breaker according to claim 1, wherein said circuit is activated by detecting a ground fault in said arithmetic circuit.
An operation output contact for generating a cutoff signal to the operation circuit, and an operation output contact when only the test signal is input to the arithmetic circuit.
Activated to suppress the output of the shut-off signal to the circuit breaker.
A ground fault directional joint having an operation lock contact
Electrical appliances.