JPH099480A - Automatic monitoring device for protection relay input circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] Three-phase input A, B, C input circuit 1 of a power system protection relay that detects an extremely small reverse current relative to the rated current.
The presence or absence of abnormality in A, 1B, and 1C is automatically monitored (self-diagnosis). [Structure] Outputs 11A-1 of input circuits 1A-1C each consisting of a CT for detecting a reverse current and an amplifier for increasing the current detection voltage thereof.
1C is a three-phase input AC that is close to the rated current of the system under normal conditions.
Exceeds full scale by. Here, the level detection circuits 12A to 12C output "1" when the inputs 11A to 11C respectively exceed the full scale, and the level difference monitoring circuit 1
3 outputs the signal 13a of "1" when the difference between the maximum value and the minimum value of the amplitude of the inputs 11A to 11C exceeds a predetermined level.
Therefore, when at least one of the three-phase inputs A to C exceeds the level corresponding to the full scale, the OR gate output 14a becomes "1".
When the output 13a of the level difference monitoring circuit is "1", the AND gate 15 issues the alarm output ALM of "1" to notify the abnormality of the input circuit 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection relay device for taking in and measuring electric quantities such as voltage and current of a power system, controlling equipment for system protection, or detecting occurrence of an accident in the system. The present invention relates to a device for automatically monitoring an abnormality in an input circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

[0002]

2. Description of the Related Art A protection relay, which operates by detecting the direction of a current flowing through a power system, takes in a voltage and a current from the power system and compares the phases of the voltage and the current. For example, the protection relay installed in the spot network power receiving system,
In order to detect the reverse current flowing from the power receiving point to the power system side, the phase characteristic as shown in FIG. 2 is provided.

That is, FIG. 2 shows the relationship between the existence region of the current vector with respect to the voltage (horizontal axis, rightward) vector and the non-operating (non-responsive) region and the operating (responsive) region of the protection relay.
That is, the lead and lag phases 0 to 90 ° with respect to the voltage (first, first
The current in the non-diagonal area of the fourth quadrant) is in the inoperative area of the protection relay, and the lead and lag phases are 90 to 180 ° with respect to the voltage.
The current in the shaded area in the second and third quadrants is in the operating area of the protection relay.

The current (reverse current) in the operating region of FIG. 2 is, for example, the reverse exciting current of the transformer or the charging current of the cable, which is generally 0.05% to several% of the rated current. On the other hand, the current in the non-operating region (forward current) is the load current, which is usually less than the rated current, but much larger than the reverse current. The current input circuit of the protection relay is designed with high sensitivity so that reverse current detection in the operating region is possible, and generally about 2% of the rated current is the full scale. Therefore, when the protection relay does not operate, that is, when the power system is healthy, the current input to the input circuit of the protection relay exceeds the full scale due to the normal load current.

[0005]

Aside from the detection of the reverse current, a protection relay which is required to have high reliability constantly monitors the presence / absence of an abnormality in its own input circuit for detecting a current input and self-diagnoses. It is desirable to do. Generally, as a method for detecting a failure of an input circuit of three-phase electric quantity, there is a method of monitoring the balance degree of a three-phase balanced input, and FIG. 3 shows the monitoring of such an input circuit of three-phase electric quantity. An example of the circuit configuration is shown. Three-phase inputs (current inputs in this example) are input to input circuits 1 (1A, 1B, 1C) each consisting of CT and an amplifier for increasing the current detection voltage, and outputs 11A to 11C is vector-synthesized by the adder circuit 2 and input to the monitoring circuit 3. The monitoring circuit 3 monitors the magnitude of the vector composite value, and when the magnitude is equal to or larger than a certain value, it judges that the input circuit 1 is defective and outputs an alarm ALM.

In FIG. 4, since the inputs of the three phases A, B and C do not exceed the full scale, the outputs 11A to 11C of the input circuits 1A to 1C.
The output waveform of the input circuit and the output waveform of the adder circuit 2 when 11C is a sine wave when the three-phase inputs are balanced are shown below.
In such a case, the output of the adder circuit 2 is zero and the alarm ALM
Is not output. On the other hand, FIG. 5 shows each of the input circuits 1A, 1A when the inputs of the three phases A, B, C exceed the full scale (that is, when the power system is normal and the protection relay is not operating).
Waveforms of outputs 11A to 11C of 1B and 1C, and an adder circuit 2
Shows the output waveform of. In this case, since the amplifiers forming the input circuits 1A to 1C are saturated and the output waveform becomes a square wave,
The output of the adder circuit 2 does not become zero, an alarm ALM is output, and even if the three-phase inputs A, B, and C are balanced, unnecessary defects are detected, and the circuit of FIG. 3 is adopted. It is not possible.

Therefore, it is an object of the present invention to provide an automatic monitoring device for a protection relay input circuit which can detect the presence or absence of an abnormality in the input circuit even when the three-phase input exceeds the full scale.

[0008]

In order to solve the above-mentioned problems, the automatic monitoring device according to the first aspect provides a voltage or current (three-phase inputs A, B, C, etc.) of a power system. An electric quantity signal (input circuit outputs 11A to 11C) which is proportional to the input electric quantity and is saturated at a predetermined value when the input electric quantity exceeds a predetermined full scale level. Input circuits (1A-
1C) is a device for automatically monitoring an abnormality of this input circuit in a protection relay having a level for detecting that at least one of the electric quantity signals output from each of the input circuits exceeds a full scale level. Detecting means (level detecting circuits 12A to 12C, OR gate 14) and level difference detecting means (level difference monitoring circuit) for detecting that the difference between the maximum value and the minimum value of the amplitude of each electric quantity signal exceeds a predetermined value. 1
3) and 2 of the level detecting means and the level difference detecting means
It is judged that the input circuit is abnormal based on two detections, and an alarm (A
And a means (AND gate 15) for outputting LM).

An automatic monitoring device according to a second aspect is the automatic monitoring device according to the first aspect, wherein the plurality of input circuits are three.

[0010]

In a protection relay device having two or more input circuits and constantly receiving an electric quantity exceeding the full scale,
If the output of one or more input circuits exceeds the full scale and the difference between the maximum and minimum values of the output swing of each input circuit exceeds the allowable range, it is determined that the input circuits are defective and an alarm is output. .

[0011]

1 is a block circuit diagram showing the configuration of an embodiment of the present invention. In the figure, the input circuit 1 (1A
1A to 11C) have the same configuration as in FIG.
C is the output of each input circuit. Also 12 (12A ~
12C) are outputs 11A-1 of the input circuits 1A-1C, respectively.
A level detection circuit that outputs a signal "1" when the level of 1C exceeds a predetermined level (in this case, full scale), a level difference monitoring circuit 13 that monitors the level difference of the three input signals 11A to 11C, 14 is a level detection circuit 12A
An OR gate for obtaining a logical sum of three detection outputs of .about.12C, and an AND gate for obtaining a logical product of the output 14a of the OR gate 14 and the output 13a of the level difference monitoring circuit 13.

To explain the operation of FIG. 1, the three-phase input A,
B and C pass through the input circuits 1A, 1B and 1C, respectively, and the outputs 11A, 11B and 11C of the respective input circuits are input to the level detection circuits 12A, 12B and 12C on the one hand and the level difference monitoring on the other hand. It is input to the circuit 13. Here, by the level detection circuits 12A, 12B, 12C, any one of the three-phase inputs A, B, C is input circuits 1A, 1B,
When the level corresponding to the full scale of 1C is exceeded, the output of the level detection circuit 12 corresponding to that phase becomes "1", and the output of the OR gate 14 which receives the detection outputs of the three level detection circuits 12A, 12B and 12C. The output 14a becomes "1".

On the other hand, the level difference monitoring circuit 13 monitors the difference between the maximum value and the minimum value of the amplitudes of the three input signals 11A, 11B and 11C, and when the difference is a certain value or more, the signal 13a of "1". Is output. Therefore, when any one of the outputs 11A to 11C of the input circuits of the three-phase inputs A to C exceeds the full scale and the difference between the maximum value and the minimum value of the amplitude of the outputs 11A to 11C is equal to or more than the predetermined value, The AND gate 15 judges that the input circuit 1 is defective and outputs the alarm output ALM of "1".

However, when none of the outputs 11A to 11C of the input circuits for the three-phase inputs A, B, and C exceeds the full scale, the output 14a of the OR gate 14 is "0", and the level difference monitoring is temporarily performed. The signal 13a of "1" from the circuit 13
Is output, the AND gate 15 does not issue the alarm output ALM of "1". As described above, in the circuit of FIG. 1, the output 13a of the level difference monitoring circuit 13 is locked so as to prevent unnecessary defect detection due to a slight imbalance of the three-phase inputs A, B, and C.

[0015]

According to the present invention, at least one output of a three-phase input circuit in which the output is saturated at all times due to an input exceeding the level corresponding to the full scale exceeds the full scale, and this three-phase input is used. When the difference between the maximum and minimum amplitudes of the three outputs of the circuit exceeds a specified value, the three-phase input circuit determines that it is abnormal and outputs an alarm.
It is possible to automatically monitor the input circuit of the protection relay that exceeds the full scale.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of an operation area of a protection relay that detects a reverse current.

FIG. 3 is a block diagram showing the configuration of a monitoring circuit of a normal three-phase input circuit.

FIG. 4 is a waveform diagram showing the operation when the 3-phase input shown in FIG. 3 does not exceed the level corresponding to full scale.

5 is a waveform diagram showing the operation when the 3-phase input shown in FIG. 3 exceeds the level corresponding to full scale.

[Explanation of symbols]

 A, B, C 3-phase input 1 (1A to 1C) input circuit 11A to 11C Input circuit 1A to 1C output 12 (12A to 12C) Level detection circuit 13 Level difference monitoring circuit 13a Level difference monitoring circuit output 14 OR gate 14a OR gate output 15 AND gate ALM alarm output

Claims (2)

[Claims] 1. A voltage or current of a power system (hereinafter, the voltage and the current are collectively referred to as an electric quantity) is input, and is proportional to the input electric quantity, and the input electric quantity has a predetermined full scale level. A device for automatically monitoring an abnormality of an input circuit in a protection relay having a plurality of input circuits that output an electric signal that saturates at a predetermined value when exceeded, which is an electric signal output from each of the input circuits. And a level difference detecting means for detecting that the difference between the maximum value and the minimum value of the amplitude of each electric quantity signal exceeds a predetermined value. An automatic monitoring device for a protection relay input circuit, comprising: means for judging an abnormality in an input circuit based on two detections of the level detecting means and the level difference detecting means and outputting an alarm. 2. The automatic monitoring device according to claim 1, wherein the plurality of input circuits are three.