JPH07174809A - Partial discharge measuring method - Google Patents

Abstract

PURPOSE:To easily specify a partial discharge occuring spot in an electric power cable by detecting partial discharge signals at a plurality of signal detecting points and comparing the detection time of each point. CONSTITUTION:A first signal detecting point 11 is an insulated connection part 2. A second signal detecting point 12 and a third signal detecting point 13 are edge cut parts 8, 9 which are the cut edges of a metal sheath 1b of an electric power cable 1 in both sides of the point 11. At first, whether partial discharge occurs or not is detected at the point 11. In the case there occurs the partial discharge, partial discharge signals are detected based on the potential difference produced in both ends of detection impedances 4b, 4c. The signals are respectively tuned in a prescribed frequency and amplified in tuning and amplifying parts 5b, 5c and sent to an oscilloscope 6. The detection time of the partial discharge signals at each of the points 12, 13 is measured, the detection time is compared with each other, and based on the time difference and an internal gap, a partial discharge occuring spot is specified.

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 capable of specifying a partial discharge occurrence point.

[0002]

2. Description of the Related Art In the partial discharge measurement of a power cable, for example, as shown in FIG. 2, a detection foil electrode 3 for electrostatic coupling provided at both ends of an insulating cylinder of an insulating connection portion 2 of a power cable 1 is used. , A detection impedance 4 connected between the detection foil electrodes 3, a tuning amplification unit 5 that tunes and amplifies a signal detected by the detection impedance 4 to a predetermined frequency, and an oscilloscope 6 that monitors the amplified signal.
And are used. To determine whether or not partial discharge has occurred, in general, the operator monitors the detected signal waveform with the oscilloscope 5, and considers that the discharge charge amount and the occurrence frequency of the partial discharge pulse change depending on the applied voltage value. At the same time, the judgment is based on whether or not a pulse is observed around the peak value of the applied voltage.

[0003]

However, in the above-mentioned partial discharge measuring method, it is possible to judge whether or not partial discharge has occurred, but whether the partial discharge specifically occurs in the insulating connection portion, There was a problem that it was not possible to identify if it occurred in the middle of the cable.

Therefore, it is an object of the present invention to provide a partial discharge measuring method capable of easily specifying the location of occurrence of partial discharge in a power cable.

[0005]

In order to solve the above problems, the present invention detects the presence or absence of a partial discharge signal generation from an insulating connection portion in a power cable line, and when the partial discharge generation is detected, the insulation is performed. Partial discharge signals are detected from two signal detection points provided at predetermined intervals on both sides of the connection part, and the detection time of the partial discharge signal at the two signal detection points is calculated to determine the detection time of the two signal detection points. There is provided a partial discharge measuring method characterized in that the partial discharge generating section is specified based on a time difference and an interval calculated by comparing detection times of partial discharge signals.

In the present invention, the presence or absence of the partial discharge signal generation is detected from the insulation connection portion in the power cable line, and when the partial discharge generation is detected, a predetermined space is provided on both sides of the insulation connection portion. Partial discharge signals are detected from two signal detection points, which are composed of edging parts that cut the metal sheath of the provided power cable, and the detected partial discharge signals are input to the signal observing section to obtain the detection time of the partial discharge signals. There is provided a partial discharge measuring method characterized in that the partial discharge generating section is specified based on a time difference and an interval calculated by comparing detection times of partial discharge signals at two signal detection points.

The above-mentioned two signal detection points and the signal observation section are
After the calibration pulse injected from the insulation connection part is detected at two detection points, the two detected calibration pulses are connected by a lead wire of a length that can be observed by the signal observation part at the same time. .

When the detection times of the partial discharge signals detected at the two signal detection points are the same, it is determined that the partial discharge generation section is the insulation connection section and its vicinity, and one of the signal detection points is detected. When the detection time of the detected partial discharge signal is earlier than the detection time of the partial discharge signal detected at the other signal detection point, the partial discharge generation unit determines that the detection time of the partial discharge signal is earlier than the signal detection point. It is determined that the detection time of the partial discharge signal is between the insulation connection portions or between the previous signal detection point and the detection time of the partial discharge signal is between the power cable termination portion on the previous signal detection point side.

If the detection time of the partial discharge signal detected at one of the signal detection points is earlier than the detection time of the partial discharge signal detected at the other signal detection point, the insulation connection portion and the partial discharge signal are detected. The partial discharge signal is detected at the earlier signal detection point, the detected partial discharge signal is input to the signal observation unit to detect the partial discharge signal detection time, and the partial discharge signal detection time is the same. In some cases, the partial discharge generation unit detects that the detection time of the partial discharge is between the previous signal detection point and the detection time of the partial discharge signal is between the power cable termination section on the side of the previous signal detection point, and is detected. When the partial discharge signals are detected at different times, the partial discharge generation unit determines that the detection time of the partial discharge signal is between the previous signal detection point and the insulating connection unit.

At the signal detection point and the insulation connection portion whose detection time of the partial discharge signal is earlier, the calibration pulse injected from the signal detection point whose detection time of the partial discharge signal is earlier is earlier than the detection time of the partial discharge signal. After being detected at the signal detection point and the insulation connection part, the two detected calibration pulses are connected by a lead wire having a length that can be observed by the signal observation part at the same time.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an apparatus configuration for carrying out the partial discharge measuring method of the present embodiment. In the present embodiment, the partial discharge occurrence point is specified by detecting signals at three signal detection points. The first signal detection point 11 is the insulation connection portion 2, and the insulation connection portion 2
The detection foil electrodes 3a provided on the anticorrosion layers 2b at both ends of the insulating cylinder 2a in FIG. 1, the detection impedance 4a connected between the detection foil electrodes 3a, and the signal detected by the detection impedance 4a are tuned to a predetermined frequency. A tuning amplifier 5a for amplifying the signal and an oscilloscope 6 for displaying the signal waveform subjected to the tuning amplification. The second and third signal detection points 12 and 13 are edging portions 8 and 9 obtained by edging the metal sheath 1b of the power cable 1 on both sides of the first signal detection point 11, respectively. The detection foil electrodes 3b and 3c provided on the sandwiched metal sheath 1b, the detection impedances 4b and 4c connected between the detection foil electrodes 3b and 3c, and the signals detected by the detection impedances 4b and 4c are respectively given to predetermined values. Tuning amplifiers 5b and 5c that tune to a frequency and amplify the frequency
And a common oscilloscope 6 and a first signal detection point 11 for displaying a tuned and amplified signal waveform. A calibration pulse generator 20 is connected to the first signal detection point 11 to the insulation connection portion 2 via a foil electrode.

[0012] The second and third signal detection points 1
The distance L ₁ L ₂ from the first signal detection point 11 of 2 and 13
Are equal to each other, and the second and third signal detection points 1
Signal lead wire 10 connecting the oscilloscope 5 with the signal wires 2 and 13
The lengths b and 10c are also equal to each other. Further, in the tuning amplifiers 5a, 5b and 5c, a frequency with a high S / N is selected and the signal is tuned to this frequency.

Next, a method of identifying a partial discharge occurrence point by using the partial discharge measuring method of this embodiment will be described. First,
At the first signal detection point 11, the presence or absence of partial discharge occurrence is measured using the method described in the related art.

When it is determined from the signal detected at the first signal detection point 11 that partial discharge has occurred, the detected impedance is detected at the second signal detection point 12 and the third signal detection point 13. The partial discharge signal is detected from the potential difference between both ends of 4b and 4c. The detected partial discharge signals are tuned and amplified at a predetermined frequency in the tuning amplifiers 5b and 5c, respectively. Then, the amplified detection signals at the respective signal detection points are input to the oscilloscope 6, respectively.

For example, if the frequency bandwidth to be tuned is 100 kHz, the pulse width is 10 μsec and the pulse propagation velocity is about 200 m / μsec. In this case, assuming that the distance from the first signal detection point 11 to the second and third signal detection points 12 and 13 is L ₁ = L ₂ = 10 m, the signal path distance difference of the pulse that has entered from the cable end portion. Is 20 m, and this distance difference is 0.1 μs as time.
It becomes the difference of ec. By confirming this time difference with the oscilloscope 6, the location where the partial discharge occurs can be specified.
When the location of the partial discharge generation by the oscilloscope 6 is specified, the rise time and the slope of the pulse can be adjusted in advance by a circuit. Then, a calibration pulse is injected in advance from the calibration pulse generator 20 of the insulated connection unit 2, and the calibration pulses detected at the second and third signal detection points 12 and 13 on the oscilloscope 6 are substantially the same at the same time. If the rise in the shape and the difference in the arrival state of the pulse when the calibration pulse is injected from the edge cutting portions 8 and 9 of the cable are confirmed, the partial discharge occurrence position can be detected based on the time difference.

According to the above, the signal waveform at the second signal detection point 12 and the signal waveform at the third signal detection point 13 displayed on the oscilloscope 6 are observed,
If partial discharge signals are detected at the same time in both signal waveforms, it can be said that the distances at which the partial discharge signals propagate to the respective detection positions are equal, and therefore the partial discharge occurrence location is the insulation connection part 2 and its vicinity. Is determined.

As another case, when the detection time of the partial discharge signal detected from the third signal detection point 13 is earlier than the detection time of the partial discharge signal of the second signal detection point 12, that is, both If the signal waveform in the oscilloscope 6 is misaligned, the partial discharge signal propagates to the respective detection positions at different distances, and therefore the partial discharge occurrence point is the first signal detection point 11 (insulation connection portion 2).
Is determined to be between the third signal detection point (edge cut portion 9) or between the third signal detection point 13 and the cable end portion 6b. The second signal detection point 12
Detection time of partial discharge signal from the third signal detection point 1
Needless to say, in the case of earlier than 3, the location where the partial discharge occurs is specified to the location opposite to the above.

When it is determined that the partial discharge occurrence location is the insulation connection portion 2 and its vicinity, the insulation discharge connection portion 2 is repaired, and the location of the partial discharge generation location is almost specified.
On the other hand, the partial discharge occurrence point is between the first signal detection point 7 (insulated connection portion 2) and the third signal detection point 13 (edge cutting portion 9), or from the third signal detection point 13 to the cable end portion 7b. If it is determined that the partial discharge occurs, it is necessary to further specify the partial discharge occurrence point. In this case, the first signal detection point 11 and the third signal detection point 1
3 is used to specify the location where the partial discharge occurs. In addition, as described above, the pulses detected from the first and third signal detection points 11 and 13 are arranged such that the rise time and the gradient can be adjusted in a circuit manner. And in advance,
A calibration pulse is injected from the third signal detection point 13, and the oscilloscope 6 adjusts the length of the lead wire so that the pulses detected at both signal detection points simultaneously rise in substantially the same shape, and The difference in the arrival status of the calibration pulse injected from each measurement point is confirmed, and the generation position can be specified based on the time difference of partial discharge generation.

First, the partial discharge signal is detected at the first signal detection point 11 and the third signal detection point 13. The detected partial discharge signal is tuned and amplified at a predetermined frequency and input to the oscilloscope 6.

Then, the signal waveform at the first signal detection point 11 and the signal waveform at the third signal detection point 13 displayed on the oscilloscope 6 are observed, and a partial discharge signal is detected at the same time in both signal waveforms. In this case, since the signal propagation distances until the partial discharge signals are detected at the respective detection positions are the same, it is determined that the partial discharge occurrence points are the third signal detection point 13 and the terminal end portion 7b. . Also,
As another case, if the signal waveforms of both are slightly different, the signal propagation distance until the partial discharge signal is detected at each detection position is different. It is determined to be between the signal detection point 11 and the third signal detection point 13.

As described above, by specifying the partial discharge occurrence point in two steps, the specifying accuracy is improved.

In the above embodiment, the calibration pulse is inserted in advance to check the arrival state of the pulse from each foil electrode or the pulse is adjusted so that the pulse rises at the same time. Then, by continuously injecting the calibration pulse, it is possible to more accurately determine whether the calibration pulse and the pulse generated in any part are at the same time or different.

Further, although the above-mentioned embodiment is directed to the insulated connection portion of the power cable, the partial discharge measuring method of this embodiment can be applied by providing an edge cut portion also in the cable-only portion and the ordinary connection portion. Can be applied.

[0024]

As described above, according to the partial discharge measuring method of the present invention, signals are detected from a plurality of signal detection points,
Since it is decided to compare the difference in the detection time of the partial discharge, it is possible to easily specify the place where the partial discharge occurs in the power cable.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a conventional partial discharge measurement method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Power cable 1a Conductor 1b Metal sheath 2 Insulation connection part 2a Insulation cylinder 2b Corrosion protection layer 3, 3a, 3b, 3c Detection foil electrode 4, 4a, 4b, 4c Detection impedance 5, 5a, 5b, 5c Tuning amplification part 6, 6a , 6b, 6c Oscilloscope 7a, 7b End part 8, 9 Edge cut part 10a, 10b, 10c Signal lead wire 11 First signal detection point 12 Second
Signal detection point 13 Third signal detection point 20 Calibration pulse generator

Claims (6)

[Claims] 1. The presence / absence of a partial discharge signal generation is detected from an insulating connection portion of a power cable line, and when the partial discharge generation is detected, the insulating connection portion is provided with a predetermined space on both sides thereof. The partial discharge signal is detected from one signal detection point, the detection time of the partial discharge signal at the two signal detection points is obtained, and the detection time of the partial discharge signal at the two signal detection points is compared and calculated. A partial discharge measuring method, characterized in that a partial discharge generation part is specified based on the determined time difference and the interval. 2. The presence or absence of a partial discharge signal generation is detected from an insulating connection portion of the power cable line, and when the partial discharge generation is detected, the insulating connection portion is provided with a predetermined space on both sides thereof. A partial discharge signal is detected from two signal detection points consisting of an edge cut portion obtained by cutting the metal sheath of the power cable, and the detected partial discharge signal is input to a signal observation unit to obtain a detection time of the partial discharge signal, A method for measuring partial discharge, characterized in that the partial discharge generator is specified based on the time difference calculated by comparing the detection times of the partial discharge signals at the two signal detection points and the interval. 3. The two signal detection points and the signal observing section detect the calibration pulse injected from the insulation connection section at the two detection points, and then detect two calibration pulses at the same time. 3. The partial discharge measuring method according to claim 2, wherein the lead wires are connected to each other by a lead wire having a length that can be observed by the signal observation unit. 4. When the detection times of the partial discharge signals detected at the two signal detection points are the same, the partial discharge generation part is determined to be the insulation connection part and its vicinity, and When the detection time of the partial discharge signal detected at the signal detection point is earlier than the detection time of the partial discharge signal detected at the other signal detection point, the partial discharge generation unit includes the partial discharge signal. Between the signal detection point earlier than the signal detection point and the insulation connection section, or the power cable termination at the signal detection point earlier in the detection time of the partial discharge signal and the signal detection point earlier in the detection time of the partial discharge signal 3. The partial discharge measuring method according to claim 2, wherein the partial discharge is determined to be between parts. 5. The insulation connection when the detection time of the partial discharge signal detected at one of the signal detection points is earlier than the detection time of the partial discharge signal detected at the other signal detection point. The detection time of the part and the partial discharge signal detects the partial discharge signal at the previous signal detection point, and the detection time of the partial discharge signal is detected by inputting the detected partial discharge signal to the signal observation part, When the detection time of the partial discharge signal is the same, the partial discharge generation unit, the detection time of the partial discharge from the signal detection point earlier from the signal detection point of the power at the signal detection point side earlier When it is determined that the partial discharge signal is between the cable end portions, and the detected partial discharge signals are detected at different times, the partial discharge generation unit separates the detection time of the partial discharge signal from the earlier signal detection point and the insulation. Connection The method for measuring partial discharge according to claim 4, wherein the method is determined to be between parts. 6. The calibration pulse injected from the signal detection point earlier than the detection time of the partial discharge signal and the insulation connection portion is the calibration pulse injected from the signal detection point earlier than the detection time of the partial discharge signal. After the detection time of is detected at the previous signal detection point and the insulation connection part, the two detected calibration pulses are connected by a lead wire having a length that can be observed by the signal observation part at the same time. The partial discharge measuring method according to claim 5.