JPH1164431A - Partial discharge measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the detection accuracy of partial discharge signals, by removing the noise of a high frequency and a small amplitude other than the relatively large pulse-like external noise of a low frequency included inside detection signals. SOLUTION: An output of an external, noise detection impedance 12 is distributed to tuned amplifiers 14a-14c, an output of a partial discharge detection impedance 11 is distributed to the tuned amplifiers 13a-13c, they are tuned- amplified, and noise components synchronized with the respective outputs of the tuned amplifiers 14a-14c are removed from the respective outputs of the tuned amplifiers 13a-13c in gate circuits 15a-15c. Only simultaneously generated signals among the output signals of the gate circuits 15a-15c are extracted in a simultaneity comparator circuit 17, the signal for indicating a maximum value in the output signals of the gate circuits 15a-15c is obtained in a signal level comparator circuit 16, and the input signal of the signal level comparator circuit 16 synchronized with the output signal of the simultaneity comparator circuit 17 is outputted from the gate circuit 18 as a measurement signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a partial discharge measuring method, and more particularly to a partial discharge measuring method for detecting a partial discharge generated from a high voltage device such as an electric device or a power cable with high sensitivity.

[0002]

2. Description of the Related Art FIG. 3 shows a partial discharge measuring device corresponding to a conventional partial discharge measuring method for detecting a partial discharge generated from a power cable. In this partial discharge measuring device, the power cable 1 is provided with a connection portion 2, and a pair of metal foil electrodes 3 are attached to the connection portion 2.
A detection impedance 4 is connected to the metal foil electrode 3, and a tuning amplifier 5 and a gate circuit 6 are connected to the detection impedance 4 in series. A noise antenna 7 for detecting pulsed external noise is provided along the power cable 1, and a detection impedance 8 is connected to the noise antenna 7. A tuning amplifier 9 is connected to the detection impedance 8, and a gate circuit 6 is connected to the tuning amplifier 9. In FIG. 3, a signal from the power cable 1 is input to the detection impedance 4, but in addition to a partial discharge signal to be detected, invading pulsed external noise is also input. Detection impedance 8
Is adjusted so that the partial discharge signal is not detected,
A surrounding noise signal is input to the detection impedance 8. This noise signal is the same pulsed external noise as the pulsed external noise included in the detection impedance 4. The signals detected by the detection impedance 4 and the detection impedance 8 are tuned and amplified by the tuning amplifier 5 and the tuning amplifier 9, respectively. The gate circuit 6 operates so as to open and close the gate using the signal of the detection impedance 8 as a control signal.
When the control signal exceeds a certain level, the detection signal from the detection impedance 4 at that time is regarded as noise, the gate is closed, and the signal output is cut off. Thereby, the pulsed external noise included in the detection impedance 8 is removed, and the gate circuit 6 can output only the partial discharge signal.

[0003]

However, according to the conventional partial discharge measurement method, since noise is removed using a gate circuit, when the control signal is small, the gate circuit does not operate, and pulse external noise is generated. There is a problem that is output. If the operating level of the gate circuit is drastically reduced to avoid this, the gate circuit will operate even with steady noise, and the partial discharge signal may be interrupted, which limits the improvement of detection accuracy. Has occurred.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the detection accuracy of a partial discharge signal by removing high-frequency, small-amplitude noise in addition to low-frequency, relatively large pulse external noise contained in a detection signal. To provide a method for measuring partial discharge.

[0005]

To achieve the above object, the present invention relates to a partial discharge measuring method for measuring a partial discharge caused by deterioration of an insulator of a high voltage device such as an electric device or a power cable. Measuring the partial discharge at at least two different frequencies to generate at least two partial discharge signals, determining the synchronism of the generation timing of the at least two partial discharge signals, and generating the at least two partial discharge signals simultaneously Providing a maximum partial discharge signal of the at least two partial discharge signals to a measurement circuit when it is determined that the partial discharge signal has been measured.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a partial discharge measuring device corresponding to the partial discharge measuring method of the present invention. In this partial discharge measuring device, the power cable 1 has a connection portion 2, and a pair of metal foil electrodes 3 are attached to the connection portion 2. A partial discharge detection impedance 11 is connected to the metal foil electrode 3. Further, a noise antenna 7 for detecting pulsed external noise is provided along the power cable 1, and an external noise detection impedance 12 is connected to the noise antenna 7.

The partial discharge detection impedance 11 includes three tuning amplifiers 13a and 13 having different tuning frequencies.
b, 13c are connected. Similarly, the external noise detection impedance 12 is also connected to three tuning amplifiers 14a, 14b, and 14c having different tuning frequencies.
Each of the tuning amplifiers 13a, 13b, and 13c is connected to each of the noise gates 15a, 15b, and 15c, and receives a control signal from each of the tuning amplifiers 14a, 14b, and 14c. Gate circuits 15a, 15b, 1
5c, a signal level comparison circuit 16 and a synchronization comparison circuit 17 are connected in parallel. Signal level comparison circuit 16
Is connected to a gate circuit 18, to which an output signal of the synchronization comparator 17 is applied as a control signal.

Next, the operation of the partial discharge measuring device having the configuration shown in FIG. 1 will be described. The partial discharge detection impedance 11 receives a partial discharge signal from the power cable 1 and a pulsed external noise. The detection signal from the partial discharge detection impedance 11 is tuned to the tuned amplifiers 13a, 13b,
13c. Tuning amplifiers 13a, 13b, 13
c is set to a frequency at which the S / N (signal / noise) ratio increases, and tunes and amplifies the input signal.

On the other hand, the external noise detection impedance 12
Is supplied with a surrounding noise signal captured by the noise antenna 7. Noise signals detected by the external noise detection impedance 12 are tuned to amplifiers 14a, 14b, 14
c is distributed and input. Tuning amplifiers 14a, 14b, 14
c is configured to tune and amplify the input signal at a frequency capable of detecting only a noise signal contained in three different frequencies (partial discharge detection signal, hereinafter referred to as “S signal”).

The three types of S signals tuned and amplified by the tuned amplifiers 13a, 13b and 13c are respectively supplied to the gate circuit 15
a, 15b, and 15c. External noise signals (hereinafter, referred to as “X signals”) obtained by the tuning amplifiers 14a, 14b, and 14c are input to the gate circuits 15a, 15b, and 15c as control signals. In the gate circuits 15a, 15b, and 15c, when the control signal is input, the S signals from the tuning amplifiers 13a, 13b, and 13c are regarded as noise, the gates are closed, and the input signal is cut off to remove noise.

Next, with reference to the waveform diagram of FIG. 2, in addition to low-frequency and relatively large external noise of pulse, high-frequency and small-amplitude noise called stationary noise is effectively removed by the method of the present invention. Explain what you can do.

In FIG. 2, (a), (b), (c)
Is the signal waveform after tuned amplification of the signal from the connection 2;
(D), (e) and (f) are external noise signal waveforms input by the antenna 7, and (g), (h) and (i) are gate circuits 1
Output signal waveforms of 5a, 15b and 15c, (j) is an output signal waveform of the signal level comparison circuit 16, (k) is an output signal waveform of the synchronization comparison circuit 17, and (l) is a final signal waveform after noise removal. , (M) are application voltage signal waveforms.

As shown in (a), (b), and (c), the output signals of the tuning amplifiers 13a, 13b, and 13c include noises 25 in addition to the S signals 19, 20, and 21.
However, each noise signal 25 (tuning amplifiers 14a, 14b,
14c) to the gate circuits 15a, 15b, 15
By applying a control signal to c, (g),
The noise 25 mixed in the S signals 19, 20, and 21 as shown in (h) and (i) is removed.

The output signals of the gate circuits 15a, 15b and 15c are supplied to a signal level comparison circuit 16 and
7 are distributed and input in parallel. Signal level comparison circuit 16
Outputs the maximum value of the input S signal at each timing. When the maximum value of the signals (g), (h), and (i) input by the signal level comparison circuit 16 is obtained, the result is as shown in (j). On the other hand, the synchronization determination circuit 17 determines the synchronization of the signals, and when three signals are input at the same time, determines that the signals are partial discharge signals, and gates the gate circuit control signal 23 as shown in (k). Output to the circuit 18.

An output signal of the signal level comparison circuit 16 is input to a gate circuit 18. The gate circuit 18 opens the gate of the gate circuit 18 only when a control signal is applied from the synchronization determination circuit 17, and the partial discharge signal 24 as shown in FIG.
Is output. As a result, since the external noise signal 25 contained in the partial discharge signal 22 is completely removed as shown in (j), only the partial discharge signal 24 can be detected with high sensitivity as shown in (l). The detection accuracy is improved.

In FIG. 1, in order to make the effect of the present invention effective, the external noise detection impedance 12 does not detect the partial discharge signal, but is optimal so that only the noise signal included in the S signal can be detected. It must be installed in a location. Further, the tuning frequency of the X signal needs to be set to a frequency at which a noise signal included in the corresponding S signal is most easily detected. Further, the output period of the output signal of the synchronization determination circuit 17 needs to have a circuit configuration capable of outputting the same width as the time of the signal having the largest amplitude of the three input signals.

In the above description, the output of the partial discharge detection impedance 11 and the output of the external noise detection impedance 12 are divided into three in consideration of the device cost and accuracy, but the present invention is limited to three. Instead, the number of distributions can be any number greater than one.

[0018]

As described above, according to the partial discharge measuring method of the present invention, after removing the infrequent and relatively large pulse external noise included in the detection signal, the partial discharge detection impedance and the external noise are eliminated. A noise component synchronized with an external noise signal is removed from each of the plurality of partial discharge detection signals obtained by distributing each output of the detection impedance to a plurality and tuned and amplified by different frequencies, and removing this noise component A signal indicating the maximum value among a plurality of signals obtained by removing only the noise components and extracting the signal simultaneously generated among the obtained signals is obtained. The signal synchronized with the output signal is used as the partial discharge measurement signal, so even low-level, high-frequency noise (steady-state noise) that was difficult to remove can be removed. It so, it is possible to significantly improve the partial discharge detection accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a partial discharge measuring device corresponding to a partial discharge measuring method according to the present invention.

FIG. 2 is a waveform chart showing an operation of the partial discharge measuring device of FIG.

FIG. 3 is a block diagram showing a partial discharge measuring device corresponding to a conventional partial discharge measuring method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Power cable 2 Connection part 3 Metal foil electrode 7 Noise antenna 11 Partial discharge detection impedance 12 External noise detection impedance 13a, 13b, 13c, 14a, 14b, 14c Tuning amplifier 15a, 15b, 15c, 18 Gate circuit 16 Signal level comparison Circuit 17 Simultaneity comparison circuit

Claims (3)

[Claims] 1. A partial discharge measuring method for measuring a partial discharge caused by deterioration of an insulator of a high-voltage device such as an electric device or a power cable, wherein the partial discharge is measured at at least two different frequencies, and Generating a partial discharge signal; determining a simultaneity of generation timings of the at least two partial discharge signals; determining that the at least two partial discharge signals are simultaneously generated; A partial discharge measuring method, comprising: outputting a maximum partial discharge signal to a measuring circuit. 2. A partial discharge measuring method for measuring a partial discharge caused by deterioration of an insulator of a high-voltage device such as an electric device or a power cable, wherein the partial discharge is measured at at least two different frequencies and at least two Generating a partial discharge signal; measuring external noise around the high voltage device at at least two different frequencies to generate at least two external noise signals; at least one of the at least two external noise signals;
Interrupting at least one partial discharge signal of the at least two partial discharge signals corresponding to the at least one external noise signal when the two external noise signals are greater than a predetermined level; Determining the synchronism of the generation timing of the remaining partial discharge signals excluding at least one partial discharge signal; determining that the remaining partial discharge signals have occurred simultaneously; A partial discharge measurement method, comprising: outputting a partial discharge signal to a measurement circuit. 3. The shutoff of the at least one partial discharge signal is performed by a gate circuit that is closed using the at least one external noise signal as a control signal, and an output of the maximum partial discharge signal to the measurement circuit is: 3. The partial discharge measurement method according to claim 2, wherein the determination is performed through a gate circuit that opens a determination signal for determining that the remaining partial discharge signals are simultaneously generated as a control signal.