JPS60155982A - Partial discharge measuring apparatus - Google Patents

Abstract

PURPOSE:To enable the removal of extraneous noise in stationary waves with the cycle almost doubling the width of an internal partial discharge pulse by employing a filter circuit, a narrow band pass filter and the like made up of a delay circuit and the like. CONSTITUTION:A partial discharge pulse of a gas insulated electric appliance is detected as distinguished from a pulse due to corona discharge in the air with a detection circuit 11 having a detection circuit 14 of an RC parallel circuit with the time constant of wavetail as specified. The detection output thereof passes through a filter circuit 12 composed of circuits 21 and 26 for delaying the pulse width of a partial discharge pulse, circuits 22 and 23 for delaying that by two or three times, addition circuits 24 and 25, a multiplication circuit 27 and the like to remove continuous extraneous noise with the cycle almost doubling the pulse width. It is further processed with an output circuit 13 having a narrow band pass filter 31 with the frequency 10% lower than the center frequency. This enables the removal of extraneous noise in stationary waves with the cycle almost doubling the width of the internal partial discharge pulse thereby ensuring a better measurement of the internal partial discharge pulse.

Description

[Detailed Description of the Invention] [Technical Field to which the Invention Pertains] The present invention relates to a measuring device for detecting internal partial discharge in gas-insulated electric appliances such as gas-insulated hermetic switchgear (fJIL) (abbreviated as GiS), and particularly to electric appliances. r to cancel the steady external noise with a period approximately twice the pulse width of the internal partial discharge pulse.
The present invention relates to a measuring instrument equipped with a wave circuit section.

[Prior art and its problems]

Tunable measuring instruments and ERA measuring instruments are known as partial discharge measuring instruments that use electrical methods to detect partial discharge current pulses, but both are narrow band types with center frequencies of 400 and 150 IIG (z .

It has loose tuning characteristics with a bandwidth of 90 and 200 KHz. In general, the partial discharge current pulse inside Gi8 is a sudden pulse with a pulse width on the order of 10-9 seconds. Therefore, the measuring instrument detects a frequency component of several hundred meters included in the discharge pulse, and the internal partial discharge The pulse detection level is low and requires an amplifier with high amplification. However, in addition to internal partial discharge pulses, a mixture of external noise such as corona noise current from power transmission lines and stationary noise from broadcast radio waves flows through the measurement circuit, and the frequency components of these external noises are detected by the measuring instrument. The problem is that the portion that matches the tuning frequency is amplified and measured together with the discharge pulse, making it difficult to distinguish between the discharge pulse and external noise.

FIG. 1 is a block diagram of a conventional measurement circuit with a logic-controlled discriminator. In the figure, 2 is the capacitance of the electrical device under test connected to the power supply 1, 8 is the coupling capacitance, and the signals detected by the pair of detection coils 4 and 7 are amplified by tuned amplifiers 5 and 8, respectively, and then 6 and 9 respectively, and after being converted into a constant rectangular wave signal, the signals are input to the discrimination circuit 10. The discharge pulses flowing to the two detection coils via the two capacitances have opposite polarities, but the external noise has the same polarity. Therefore, in the discrimination circuit consisting of an AND circuit, the external noise is output to the output circuit 1. The output is blocked, and only internal discharge pulses are output to the measurement circuit, and their number and size are measured. ◎There is a problem that even if internal discharge pulses are detected, they cannot be measured. , so it has the disadvantage of being limited by the number and its size.

As mentioned above, according to the conventional technology, noise at frequencies outside the bandwidth can be easily eliminated by narrowing the band of the measuring instrument, but noise at frequencies within the bandwidth, especially stationary noise, can be easily eliminated. This poses a problem in that the partial discharge detection sensitivity of the measuring instrument cannot be increased because it is not possible to eliminate the target noise.

[Purpose of the invention]

As mentioned above, it is an object of the present invention to provide a partial discharge measurement @ capable of eliminating stationary external noise corresponding to approximately twice the pulse width of the internal partial discharge pulse of the gas-insulated device.

[Key points of the invention]

The measuring instrument of the present invention is characterized in that the pulse width of the partial discharge current pulse generated inside the gas insulated electric appliance is 10-9 seconds or less, which is steeper than the pulse width of 10-8 seconds or more of corona discharge in the atmosphere such as &D/power transmission lines. Focusing on the phenomenon of partial discharge, the wave tail time constant of the partial discharge detection section is set to, for example, 1o-9 seconds or less, and the detection signal containing various detected noises is passed through the r-wave circuit section, thereby detecting the partial discharge. By removing stationary external noise such as radio waves having a period approximately twice the pulse width of the current pulse, and passing the output signal of the f-wave circuit section through a narrow band filter provided on the output side of the r-wave circuit. Instead of converting external noise other than the radio waves into r-waves, only the internal partial discharge of the electric appliance is detected.

Furthermore, as an r-wave circuit section, a first circuit section which has an age input signal as a common input. Second. The eighth delay circuit outputs the detection signal to one times the pulse width of the partial discharge current pulse.

The phase of the stationary external noise having a period approximately twice that of the discharge pulse is shifted by a half period by a time delay corresponding to twice and eight times, and the first and second adder circuits
External noises of opposite polarity are added together to eliminate the external noise, and the first and second
The adder circuit sends a total of four partial discharge pulses to a multiplier to obtain one amplified partial discharge pulse.

[Embodiments of the invention]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before explaining the present invention based on examples, the present invention will be described in detail based on original waveforms of partial discharge pulses and external noise.

Figure 2 is an example of the waveform of partial discharge and external noise that appears in the detection unit connected to the detection end of a gas-insulated electric appliance. In the figure, it is close to the original waveform detected by the C8 parallel detection circuit with a short wave tail time constant This shows a pulse waveform. In the figure, waveform P is a partial discharge pulse waveform inside the gas-insulated electric appliance, and its pulse width is 10-9 seconds or less. A is external noise due to corona discharge of power transmission lines, B is pulsed external noise such as trigger pulses such as Cyrisk, and the pulse width is 10-
It takes about 8 seconds. C is periodic stationary noise such as broadcast radio waves and radio waves, and some of the radio waves are on the order of 10-9 seconds (several hundred megahertz), and the half period is the pulse width of the partial discharge pulse. It will be very close to. The measuring instrument of the present invention detects the detected waveform containing various noises as shown in Fig. 2 in a state close to the original waveform using a detection section with a short tail time constant. The external noises A and B can be discriminated by a filter, and the periodic external noise C whose half period is approximately equal to the pulse width of the partial discharge pulse P is removed by the r-wave circuit section.

FIG. 8 is a block diagram of a measuring instrument showing an embodiment of the invention. In the figure, 11 is a detection section, 12 is a P-wave circuit section, 1
8 is an output circuit section. The detection unit 11 has a wave tail time constant of 1
A detection circuit 14 having a resistor and capacitor (Re) parallel input circuit of 0-9 seconds or less, and a high-pass filter 15 having a cut-off frequency of several hundred KHz, for example, to which the detection signal of the detection circuit 14 is input, Low frequency noise in the detection signal is removed. The r-wave circuit section 12, which receives the output signal of the detection section 11, generates radio waves, etc., with a period approximately twice the pulse width TO (10-9 seconds) of the partial discharge pulse inside the gas-insulated electric appliance in the detection signal. The output signal of the detection section 11 is used as a common input, and when the pulse width To is delayed by 1, 2, and 8 times, respectively, one detection section 11 and the a first addition circuit 24 which receives the output signal of the first delay circuit 21; a second addition circuit 25 which receives the output signals of the second and eighth delay circuits 22 and 28; A fourth delay circuit 26 that delays the output signal of the circuit by To, and a multiplier 2 that receives output pulses from the fourth delay circuit 26 and the second addition circuit 25.
7 and Karanashi, both are composed of analog circuits. The output circuit 18 includes a narrow band filter (for example, a center frequency of 267 MHz,
(bandwidth: 6 MHz) 81, a detector 82, and a peak value voltmeter 38. It consists of a pulse counter 84, and the pulse width To
Alternatively, external noise with a pulse width or period other than stationary noise with a period approximately twice that of To is removed by the narrow band filter 31, and a partial discharge pulse that has become an oscillating waveform by passing through the narrow band filter 81 is detected. Vessel 8
2 to detect it as an envelope pulse, and measure the peak value or number of pulses of the envelope pulse.

FIG. 4 is a time chart for explaining the operation of the P-wave circuit section 120 in the above-mentioned embodiment, showing the partial discharge pulse P inside the gas-insulated electric appliance and the stationary noise with a period approximately twice the pulse width TO of the pulse P. n is shown extracted from other external noises. At the left end of each waveform, the reference numerals of each part in FIG. 8 are shown in parentheses, and are used as the reference numerals of the output signal waveform of each part. Waveform (15) is the output waveform of the high-pass filter 15, and has a pulse width To of the partial discharge pulse P.
This shows a state in which the half cycle of the stationary noise n and the stationary noise n almost match. Waveforms (21), (22), and (28) are the output waveforms of the delay circuits 21, 22, and 28, respectively, and are To compared to waveform (15).

A signal delayed by 2To + 8To is output.

Waveforms (24) and (25) are the output signal waveforms of the adder circuits 24 and 25, respectively.For example, the noise waveforms (15) n and (21) have a phase difference of 180 degrees, so the time point at which they are added is It is erased and one addition is added! From (24)) half waves at both ends of the noise n and the discharge pulse P increased by two are output. The same applies to the adder circuit 25.

The waveform (26) is the output waveform of the eighth delay circuit 26, and the comparison pulse is output with a delay of To compared to the waveform (24). The waveform (27) is the output waveform of the multiplier 27, and since the waveforms (25) and (26) are multiplied, only Pl and P2, where two pulses overlap at the same time, remain. Only a partial discharge pulse having a peak value of (PIXP2) is output to the output side of the multiplier 27. However, the output of the P-wave circuit section 11 includes various external noises whose half-periods or pulse widths deviate from TO, which are omitted in the explanation of FIG. These external noises are removed when they pass through the narrow band filter 81 of the output circuit section 18, so the detector 82 receives the partial discharge pulse (27) which has an oscillating waveform when passing through the filter 81. ) is input, and the detector 82
, a partial discharge pulse whose pulse width has been expanded by being detected is output.

External noise that cannot be removed in principle in the partial discharge measuring device configured as described above is composed of two types: random noise with a pulse width equal to the pulse width TO of the partial discharge pulse inside the gas-insulated electric device, and internal noise of the circuit elements. become a kind. The former can be dealt with by narrowing the bandwidth of the narrowband filter 81 as much as possible and by lowering the spectral density of noise. Regarding the latter, the noise level can be reduced to a considerable degree by devising a low-noise circuit.

The center frequency of the narrow band filter 81 is preferably set to a frequency as close as possible to the pulse width To of the partial discharge pulse and avoids the communication frequency band. For example, the center frequency is 267 MHz, the bandwidth is 6M1 (z Good results can be obtained if

〔Effect of the invention〕

As described above, the present invention includes a detection section having a wave tail time constant of 10" seconds or less, and an f-wave that removes stationary external noise having a half period approximately equal to the pulse width of a partial discharge pulse inside a gas-insulated electric appliance. A partial discharge measuring device was constructed by a circuit section and an output circuit section equipped with a detector and a narrowband filter with a center frequency close to the period approximately twice the pulse width of the partial discharge pulse and a narrow bandwidth.Results , it is possible to remove stationary external noise with a frequency close to the pulse width (frequency component) of the partial discharge detection pulse, which was difficult to do in the past, and to remove external noise with a different frequency component. It is possible to provide a partial discharge measuring device that can be removed by a bandpass filter.

In addition, by setting the wave tail time constant of the detection section to a short time constant with little distortion of the partial discharge pulse, the P-wave circuit section can be configured with an analog circuit, and high-speed signal processing can be performed using simple circuit elements. I was able to configure it.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an improved conventional partial discharge measuring circuit, FIG. 2 is a waveform diagram of partial discharge pulses and external noise, and FIG. 8 is a block diagram of a measuring instrument showing an embodiment of the present invention. FIG. 4 is a time chart of signal waveforms at various parts of the r-wave circuit section in the embodiment shown in FIG. l...Power supply, 2...Capacitance of gas insulated electric appliance, 8...Coupling capacitance, 4, 7...Detection coil, 11...Detection section, 12...R wave circuit section, 18.
... Output circuit section, 14... Detection circuit, 15... High-pass filter, 21... First delay circuit, 22...
・Second delay circuit・28...Eighth delay circuit~24・
...First addition circuit, 25...Second addition circuit, 26
... Fourth delay circuit 27... Multiplier, 31...
Narrowband filter・82...Detector, P...Partial discharge pulse, A, 13...Pulse-shaped external noise, cgn
... Steady external noise, TO... Partial discharge pulse pulse width.

Claims (1)

[Claims] 1) A measuring device that detects only the internal partial discharge of the internal partial discharge current pulse and external noise current of the electric generator connected to the partial discharge detection end of the gas-insulated electric appliance and flowing through the detection part. and an output circuit including the detection section, a P-wave circuit section that discriminately removes continuous external noise having a period approximately twice the pulse width of the internal discharge pulse, and a narrowband filter and a wave detector; The P-wave circuit section includes a first delay circuit that uses the detection signal of the detection section as a common input and has a delay time predetermined by the pulse width of the partial discharge pulse, and a circuit that is twice as long as the first delay circuit. a second delay circuit having a delay time of a second addition circuit that receives the output signals of the second and eighth delay circuits; a second addition circuit that receives the output signals of the first addition circuit and has a delay time equal to that of the first delay circuit; 1. A partial discharge measuring device comprising: a fourth delay circuit having a fourth delay circuit; and a multiplier that receives output signals from the fourth delay circuit and a second addition circuit. 2. Partial discharge measurement according to claim 1, characterized in that the detection unit includes a detection circuit consisting of R and C parallel circuits having a wave tail time constant of 10-9 seconds or less. vessel. 8) Partial discharge measurement according to claim 1, characterized in that the output circuit section comprises a detector and a narrowband filter whose bandwidth is 10% or less of the center frequency. vessel.