JP2012005200A - Three-phase voltage relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cost by reducing the number of connections of auxiliary instrument transformers while maintaining reliability of a voltage measurement.SOLUTION: A three-phase voltage relay includes: auxiliary instrument transformers 2a and 2c which measure a voltage of a main circuit; a detecting circuit 4 which is connected to the auxiliary instrument transformers 2a and 2c and detects the voltage; an A/D converter 5 which is connected to the detecting circuit 4 and digitally converts a signal; a multiplexer 6 which is connected to the A/D converter 5 and combines a plurality of signals into a single signal; and a CPU 7 which is connected to the multiplexer 6 and performs a protection operation. The auxiliary instrument transformers 2a and 2c have two phases, and the other phase is branched by an output of the auxiliary instrument transformers 2a and 2c of two phases, and each phase is input to an adder circuit 10, thereby generating the signal.

Description

  Embodiments described herein relate generally to a three-phase voltage relay that performs a protection operation in an overvoltage or undervoltage in a power distribution system.

  Conventionally, in a three-phase voltage relay of a power distribution system such as a switchgear, voltage measurement is performed by an instrument transformer connected to each phase of the three phases, and a protection operation in case of overvoltage or undervoltage has been performed (for example, , See Patent Document 1).

  A three-phase voltage relay of this type is shown in FIG. 3, and the R, S, T phase main circuit is connected to the first to third main circuit instrument transformers 1a, 1b, 1c for each phase. Yes. The outputs of the first to third main circuit instrument transformers 1a, 1b, and 1c include first to third auxiliary instrument transformers 2a, 2b that measure the voltage of each phase provided in the relay. 2c is connected.

  The first to third filter circuits 3a, 3b, and 3c are connected to the outputs of the first to third auxiliary instrument transformers 2a, 2b, and 2c, respectively, and noise cut is performed. Outputs of the first to third filter circuits are input to a detection circuit 4 that detects a voltage, and converted into a digital signal by an A / D converter 5. This signal is input to the CPU 7 via the multiplexer 6 that outputs the three-phase signals together, and the voltage value of each phase is calculated. If an overvoltage or undervoltage exceeding the set value is reached, the protection operation is executed.

JP 2000-354324 A (FIG. 1)

  In the above-described conventional three-phase voltage relay, the first to third auxiliary instrument transformers 2a, 2b, and 2c are connected to measure the voltage of each phase, so there is a limit to cost reduction. . In particular, the first to third auxiliary instrument transformers 2a, 2b, and 2c are high-accuracy with few errors, and thus cost is high.

  The present invention has been made to solve the above-mentioned problems, and provides a three-phase voltage relay that reduces the number of connected auxiliary instrument transformers while maintaining the reliability of three-phase voltage measurement, thereby reducing the cost. The purpose is to do.

  In order to achieve the above object, a three-phase voltage relay of the present invention includes an auxiliary instrument transformer for measuring a voltage of a main circuit, a detection circuit for detecting a voltage connected to the auxiliary instrument transformer, An A / D converter for digitally converting a signal connected to the detection circuit, a multiplexer for combining a plurality of signals connected to the A / D converter, and a protection operation connected to the multiplexer are executed. A three-phase voltage relay comprising a CPU, wherein the auxiliary instrument transformer is for two phases, and the remaining phases branch the output of the auxiliary instrument transformer for the two phases and add it to the adder circuit A signal is generated by inputting each of them.

The figure which shows the circuit structure of the three-phase voltage relay which concerns on Example 1 of this invention. The figure which shows the circuit structure of the three-phase voltage relay which concerns on Example 2 of this invention. The figure which shows the circuit structure of the conventional three-phase voltage relay.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, a three-phase voltage relay according to Embodiment 1 of the present invention will be described with reference to FIG. 1 is a diagram illustrating a circuit configuration of a three-phase voltage relay according to a first embodiment of the present invention. In FIG. 1, the same components as those in the prior art are denoted by the same reference numerals.

  As shown in FIG. 1, first to third main circuit instrument transformers 1a, 1b, and 1c are connected to each phase of the R, S, and T phase main circuits. The outputs of the first to third main circuit instrument transformers 1a, 1b, and 1c include a first auxiliary instrument transformer 2a that measures the voltage provided in the relay, and a third auxiliary instrument transformer. A device 2c is connected.

  That is, the first auxiliary instrument transformer 2a is connected to the outputs of the first and second main circuit instrument transformers 1a and 1b, and voltage measurement of the R phase (between the R and S phases) is performed. The third auxiliary instrument transformer 2c is connected to the outputs of the third and first main circuit instrument transformers 1c and 1a, and voltage measurement in the T phase (between the T and R phases) is performed. The outputs of the first and third auxiliary instrument transformers 2a and 2c are noise-cut by the first and third filter circuits 3a and 3c, respectively, and input to the detection circuit 4 that detects the voltage.

  Further, the outputs of the first and third auxiliary instrument transformers 2a and 2c are branched in both phases and input to an adder circuit 10 for adding signals to measure the voltage of the S phase (between the S and T phases). Is called. The output of the adder circuit 10 is noise-cut by the second filter circuit 3 b and input to the detection circuit 4. The adder circuit 10 is configured by hardware in which electronic components such as resistors and capacitors are combined.

  The output of the detection circuit 4 is input to the A / D converter 5 and converted into a digital signal. This signal is input to the CPU 7 via the multiplexer 6 that outputs the three-phase signals together. In the CPU 7, the voltage value of each phase is calculated. If an overvoltage or undervoltage exceeding the set value is reached, the protection operation is executed.

  As a result, the voltage for three phases can be measured by the first and third auxiliary instrument transformers 2a, 2c and the adder circuit 10, so that expensive components (conventional second auxiliary instrument transformer 2b ) Can be reduced. Further, since the S-phase signal is generated by the adder circuit 10, the protection operation can be executed while maintaining the reliability. Since the adder circuit 10 is configured by hardware, noise resistance is improved as compared with that configured by software.

  Here, the CPU 7 adds a function of performing a 2 out of 3 operation to execute a protection operation when two phases out of the three phases exceed a set value, so that one phase portion up to the detection circuit 4 is added. Unnecessary operation due to failure of electronic components can be prevented. In addition, by adding a function that performs 3UV AND operation to perform protection operation when all three-phase voltages exceed the set value, unnecessary operation due to failure of electronic components for one phase up to the detection circuit 4 Can be prevented.

  In addition, when there is little noise in the main circuit, and further noise transfer countermeasures are taken inside the first and third auxiliary instrument transformers 2a and 2c, the first to third filter circuits 3a, 3b and 3c can be omitted.

  According to the three-phase voltage relay of the first embodiment, the adder circuit 10 is configured such that the first and third auxiliary instrument transformers 2a and 2c are connected to the R phase and the T phase, and the S phase is configured by hardware. Therefore, the number of parts can be reduced and the cost can be reduced while maintaining the reliability of the protection operation in the CPU 7.

  Next, a three-phase voltage relay according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2 is a diagram illustrating a circuit configuration of the three-phase voltage relay according to the second embodiment of the present invention. The second embodiment is different from the first embodiment in the position where the adder circuit is connected. In FIG. 2, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 2, the branched outputs of the first and third auxiliary instrument transformers 2a and 2c are input to the adder circuit 10 via the fourth and fifth filter circuits 3a1 and 3c1, respectively. Yes. In the adder circuit 10, an S-phase signal is generated and input to the detection circuit 4.

  According to the three-phase voltage relay of the second embodiment, in addition to the same effects as those of the first embodiment, the signal input to the adder circuit 10 has less noise, and the accuracy of the generated signal can be improved. .

  According to the embodiment described above, voltage measurement for three phases is performed by the auxiliary instrument transformer and the addition circuit for two phases, so that the number of parts can be reduced and the cost can be reduced.

  Several embodiments have been described above, but these embodiments are merely given as examples and are not intended to limit the scope of the present invention. Indeed, the novel circuits described herein may be embodied in various other forms, and various omissions may be made in the form of circuits described herein without departing from the spirit or spirit of the invention. Replacements and changes may be made. The appended claims and their equivalents are intended to include such forms or modifications as would fall within the scope and spirit or spirit of the present invention.

1a, 1b, 1c Main circuit instrument transformers 2a, 2b, 2c Auxiliary instrument transformers 3a, 3b, 3c, 3a1, 3c1 Filter circuit 4 Detection circuit 5 A / D converter 6 Multiplexer 7 CPU
10 Adder circuit

Claims (5)

An auxiliary instrument transformer for measuring the voltage of the main circuit;
A detection circuit for detecting a voltage connected to the auxiliary instrument transformer;
An A / D converter for digitally converting a signal connected to the detection circuit;
A multiplexer for combining a plurality of signals connected to the A / D converter into one;
A three-phase voltage relay comprising a CPU for performing a protection operation connected to the multiplexer,
The auxiliary instrument transformer is for two phases,
For the remaining phases, the output of the auxiliary instrument transformer for two phases is branched and input to an adder circuit to generate a signal, which is a three-phase voltage relay.   The three-phase voltage relay according to claim 1, wherein a filter circuit is connected to each of an output side of the auxiliary instrument transformer and an output side of the adder circuit.   The three-phase voltage relay according to claim 1, wherein a filter circuit is connected to each of an output side of the auxiliary instrument transformer and an input side of the adder circuit.   4. The three-phase voltage relay according to claim 1, wherein the CPU has a 2 out of 3 function. 5.   The three-phase voltage relay according to any one of claims 1 to 4, wherein the CPU is provided with a 3UV AND function.

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