JP2951523B2 - Partial discharge measurement method for power cable lines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of measuring a partial discharge of a power cable line, and more particularly to a method of measuring a partial discharge signal and noise in a power cable line capable of performing highly accurate measurement. The present invention relates to a discharge measurement method.

[0002]

2. Description of the Related Art As a method of measuring a partial discharge of a power cable line, conventionally, a foil electrode and a detection impedance are attached to an intermediate insulating connection portion of the power cable line, and a partial discharge pulse generated when a partial discharge occurs is detected by the foil electrode. It was measured by impedance, and its waveform, frequency, and the like were visually observed by a human using a waveform observation device such as an oscilloscope or a spectrum analyzer, and empirically distinguished between a partial discharge signal and noise.

[0003]

In the above-described prior art, a human must be present at the time of measurement, and a quantitative determination cannot be made. For this reason, there has been a problem that accuracy is poor and much time is required. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a method for automatically identifying noise intruding from the outside, thereby improving accuracy. Is to perform a partial discharge measurement with a high value.

[0004]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention relates to a power supply for measuring a partial discharge generated in an insulated connection portion or a power cable line on both sides of the insulated connection portion. In the partial discharge measurement method of the cable line, for the signal measured at the insulated connection,
The frequency characteristic A (f) of the signal strength is obtained, and the obtained frequency characteristic A (f) is corrected by the following equation using a transfer function C (f) corresponding to the distance between the measurement point and the partial discharge occurrence point. Amended
Frequency characteristic A 'seeking (f), A' and (f) = A (f) / C (f) corrected frequency characteristic A '(f), a frequency characteristic that model previously measured partial discharge Is determined, and when the similarity between the two is within a predetermined range, it is determined that the measured signal is a partial discharge signal.

[0005] According to a second aspect of the present invention, an insulated connecting portion is also provided.
Or power cable lines on both sides of the insulation connection
Partial discharge of power cable line to measure generated partial discharge
In the method, the transfer function of the signal propagation in the power cable line C (f) is to previously obtain each distance, the
For the signal measured at the insulated connection,
Numerical characteristics A (f) are obtained, and the obtained frequency characteristics A (f) are
From the transfer function C (f) , the frequency characteristic A '(f) at each distance is obtained by correction using the following equation. A' (f) = A (f) / C (f) The degree of similarity between each frequency characteristic obtained and the frequency characteristic serving as a model of the partial discharge measured in advance is determined. When the similarity of the highest similarity is within a predetermined range, the above-described measurement is performed. Is determined to be a partial discharge signal, and the distance between the measurement point and the location where the partial discharge occurs is estimated from the transfer function C (f) having the frequency characteristic with the highest similarity.

[0006]

FIG. 1 is a diagram showing an example of the frequency characteristic of a noise signal and the frequency characteristic of a partial discharge signal. FIG. 1A shows the frequency characteristic of a noise signal, and FIG. 1B shows the frequency characteristic of a partial discharge signal. Is shown. In FIG. 3B, A is the frequency characteristic obtained by injecting a simulation pulse into the power cable, and D is the frequency characteristic of the actual partial discharge pulse measured in the laboratory. As is clear from the figure, there is a clear difference between the frequency characteristics of (a) and (b).

Therefore, the frequency characteristic of the measured signal is determined, the determined frequency characteristic is compared with the frequency characteristic of the model partial discharge signal, and the similarity is examined to determine whether the measured signal is a partial discharge signal. Can be determined. Further, when the partial discharge is generated in a distant place, the frequency characteristic changes while the partial discharge signal propagates to the measurement point. Therefore, when it is estimated that the partial discharge is occurring in a distant place, the frequency characteristic of the measured signal is
By correcting with the transfer function of the signal propagation path from the partial discharge occurrence point to the measurement point, similarity with the frequency characteristic of the partial discharge signal to be a model can be obtained.

The similarity can be obtained by the following method. (i) Normalization Let the frequency characteristic of the measured signal be A (f) and the frequency characteristic of the partial discharge signal be D (f). The average value of A (f) in the measurement frequency range f1 to f2 is Ave.
The average value of (f) is defined as Ave. (D), and A (f) and D
(F) is normalized to obtain B (f) and E (f), respectively.

B (f) = A (f) / Ave. (A) (1) E (f) = D (f) / Ave. (D) (2) (ii) Calculation of similarity The ratio of B (f) and E (f) obtained from (1) and (2) is obtained, and “1” is subtracted to calculate an integral value by the following equation (3). Find out.

[0010]

(Equation 1)

When R obtained by the above equation (3) is smaller than a predetermined set level, the frequency characteristic A (f) of the measured signal is similar to the frequency characteristic D (f) of the partial discharge signal, When R is larger than a predetermined set level, the frequency characteristic A (f) of the measured signal and the frequency characteristic D (f) of the partial discharge signal can be considered to be dissimilar.

(Iii) When partial discharge is generated in a distant place When a partial discharge pulse propagates in a cable, the frequency characteristic changes. If the transfer function of the partial discharge pulse is known in advance, the measured signal The frequency characteristic A (f) can be corrected. That is, when a partial discharge is generated in a distant place, assuming that the transfer function of the signal propagation path from the partial discharge occurrence point to the measurement point is C (f), the frequency characteristic A (f) of the measured signal is expressed by the following equation. It can be corrected by (4). A ′ (f) = A (f) / C (f) (4) Then, a frequency characteristic A ′ (f) is obtained from the frequency characteristic A (f) of the measured signal. the above
By the methods shown in (i) and (ii), the similarity with the partial discharge signal serving as a model can be obtained.

According to the present invention, there is provided a power cable based on the above principle.
It is designed to measure partial discharge in a line.
In the invention of claim 1 of the present invention,
For the measured signal, the frequency characteristic A of the signal strength
(F) is determined and the determined frequency characteristic is obtained.A (f)With the measuring point
Transfer function according to the distance between partial discharge occurrence pointsC (f)
AndAccording to the above equation (4)Corrected and corrected frequency characteristics
Find A '(f),Corrected frequency characteristicsA '(f)
And the frequency characteristics that become the model of the partial discharge measured in advance
The similarity between the two is calculated, and the similarity between
When within the box, the measured signal is a partial discharge signal
Was determined to be present, so the location of the partial discharge was measured.
Automatically generates noise and partial discharge signals even when away from a fixed point
To perform highly accurate partial discharge measurements.
You.

According to the second aspect of the present invention, a transfer function C (f) of signal propagation in a power cable line is obtained for each distance, and the transfer function C (f) is measured at the insulated connection.
For the signal, a frequency characteristic A (f) of the signal strength is obtained,
The obtained frequency characteristic A (f) is corrected from the transfer function C (f) by the above equation (4), and the frequency characteristic at each distance is corrected.
A ′ (f) is calculated, and the degree of similarity between each frequency characteristic corrected by the transfer function and the frequency characteristic that is a model of the partial discharge measured in advance is calculated. When the similarity is within a predetermined range, it is determined that the measured signal is a partial discharge signal, and the measurement point and the partial discharge occurrence are determined from the transfer function C (f) having the frequency characteristic with the highest similarity. Since the distance between the points is estimated, the same effect as that of the first aspect of the invention can be obtained, and the distance between the measurement point and the partial discharge occurrence point can be estimated.

[0015]

FIG. 2 is a diagram showing the configuration of a measurement system according to an embodiment of the present invention. In FIG. 2, reference numeral 11 denotes a 275 kV C
This is a V cable, and three-phase two-circuits are laid inside the tunnel. Reference numeral 12 denotes an intermediate insulated connection,
2 are provided about every 500 m. The intermediate connection part is an insulated connection part in which two of the three are insulated from the sheath shown in FIG.

Reference numeral 12a denotes a simulated pulse generator. The simulated pulse generator 12a is connected to the foil electrodes 12b attached to both sides of the sheath insulating portion of the intermediate insulating connecting portion 12, and is connected to the intermediate insulating connecting portion via the foil electrode 12b. A simulation pulse is injected into 12. Reference numeral 12c denotes a partial discharge detector, and the partial discharge detector 12c is connected to foil electrodes 12b 'attached to both sides of the sheath insulating portion.

The foil electrodes 12b and 12b 'are obtained by attaching a rubber sheet to the outside of a 250 mm square aluminum foil.
Since the outside of the protective copper tube of the intermediate insulating connecting portion 12 is coated with an insulator for anticorrosion, a capacitance of about several hundred pF is formed between the protective copper tube and the aluminum foil.
Therefore, when the simulation pulse is generated from the simulation pulse generator 12a, the simulation pulse is injected into the intermediate insulating connection portion 12 via the above-described capacitance.

When a partial discharge occurs in the cable line, a high-frequency component of the partial discharge signal is split to the outside of the cable by the insulating portion of the sheath, and the high-frequency component is detected by the foil electrode 12b via the capacitance. Is done. The partial discharge detector 12c is mainly composed of an inductance component.
The partial discharge signal is converted into a voltage signal.

13 is an amplifier, 14 is an electro-optical converter, 15
Is an optical fiber, 16 is a photoelectric converter, 17 is a preamplifier, 18 is a spectrum analyzer, 19 is a processor, the partial discharge signal detected by the partial discharge detector 12c is amplified by the amplifier 13, and the electro-optical converter 14 Is converted into an optical signal. Then, the signal is transmitted through the optical fiber 15 and converted into an electric signal again by the photoelectric converter 16. The transmission band in this embodiment is 1 MHZ.
The frequency was set to 50 MHz from z.

The electric signal converted by the photoelectric converter 16 is amplified by a preamplifier 17 and applied to a spectrum analyzer 18 through a filter (not shown) for frequency analysis. The output of the spectrum analyzer 18 is further analyzed by the processor 19, and the result is continuously recorded by the recording device 20. In the power cable line shown in FIG. 2, a simulation pulse was injected from the simulation pulse generator 12a, and a signal was detected by the partial discharge detector 12c.

FIG. 1A shows a typical noise frequency, and FIG. 1B shows the frequency characteristic of the measurement signal obtained as described above [frequency characteristic A (f) in FIG. 〕When,
It shows the frequency characteristic of the actual partial discharge pulse measured in the laboratory [frequency characteristic D (f) in the figure], and as is apparent from FIG. 2B, the actual partial discharge pulse measured in the laboratory. And the frequency characteristic A obtained by injecting the simulation pulse are in good agreement.

The frequency characteristics A of the measurement signal obtained by injecting the simulated pulse, the noise signal of FIG. 1A, and the frequency characteristics D of the partial discharge signal are described above in (1) to (3). Were calculated, and R was obtained for each of them. The following results were obtained. For a noise signal: RN = 0.35 to 0.53 For a partial discharge signal: RN = 0.02 to 0.08 From the results above, if RSP = 0.2 is set as a set value, , (1) to (3), it was found that noise and partial discharge were distinguished.

In the partial discharge measurement according to the present embodiment,
The signal measured by the partial discharge detector 12c is analyzed by the spectrum analyzer 18 in FIG. 2, and the above-mentioned calculations (1) to (3) are performed off-line to obtain RN and compare it with the set value RSP. And whether the measured signal is a partial discharge signal or a noise.

It is also possible to automatically identify whether the signal measured online by the processor 19 is a partial discharge signal or a noise. That is, the processor 19 stores in advance the frequency characteristics of the partial discharge signal to be a model. Then, the signal detected by the partial discharge detector 12c is analyzed by the spectrum analyzer 18, and RN is calculated based on the frequency characteristics of the signal detected by the processor 19 and the frequency characteristics of the partial discharge signal as the model described above. Compared to the RSP, it automatically identifies whether the measured signal is a partial discharge signal or a noise.

By doing so, it is possible to automatically discriminate between partial discharge and noise without manual intervention, and it is possible to detect the occurrence of partial discharge with high accuracy. Next, a simulated pulse was injected from a simulated pulse generator 12a provided at an adjacent intermediate insulating connection portion 12 at a distance of about 500 m from the measurement point, and measured by a partial discharge detector 12c. Were obtained.

On the other hand, a transfer function C (f) of signal propagation between the adjacent intermediate insulating connection portion 12 and the measurement point is obtained in advance, and the measurement signal A is calculated by the transfer function C (f) according to the above equation (4). ), The result shown in A ′ (f) of FIG. 3 was obtained. As described above, with respect to the obtained A ′ (f), the calculations shown in the above equations (1) to (3) are performed, and R ′
When N was determined, partial discharge and noise could be distinguished in the same manner as described above.

From the above results, even if the measurement point and the partial discharge occurrence location are far from each other, if the transfer function between the measurement point and the partial discharge occurrence location is known, the noise and the partial discharge as described above can be obtained by the method of the present invention. It can be seen that the discharge signal can be accurately identified. Therefore, the transfer function at the time of signal propagation in the power cable line is determined in advance for each distance, and the frequency characteristics of the signal detected by the partial discharge detector 12c are described above using the transfer function determined for each distance by the processor 19 as described above. The frequency characteristics A ′ (f) are obtained by performing correction according to (4). Then, each frequency characteristic A ′
For (f), RN is calculated, and RN having the highest similarity is calculated.
By comparing with the above-mentioned set value RSP,
It is possible to distinguish between partial discharge and noise.

According to this method, the partial discharge signal and the noise can be automatically and accurately distinguished even if the location where the partial discharge occurs is far from the measurement point. Further, it is also possible to estimate the distance from the measurement point to the partial discharge occurrence point from the transfer function when RN having the highest similarity is calculated. The above-described processing can be promptly obtained without human intervention by causing the processor 19 to repeatedly calculate.

[0029]

As described above, according to the present invention, the frequency characteristic of the signal strength is obtained for the signal measured at the insulated connection part, and the obtained frequency characteristic is determined by the distance between the measurement point and the partial discharge occurrence point. The degree of similarity between the corrected frequency characteristic and the frequency characteristic that is a model of the partial discharge measured in advance is determined by the corresponding transfer function, and when the degree of similarity between the two is within a predetermined range, the above measurement is performed. Since the detected signal is determined to be a partial discharge signal, noise and partial discharge signal are automatically identified even if the partial discharge occurrence point is far from the measurement point, and highly accurate partial discharge measurement is performed. be able to.

Further, the transfer function of the signal propagation in the power cable line advance determined have respective distances Nitsu, the frequency characteristics obtained by correcting the above transfer functions, each frequency characteristic is corrected by the transfer function in advance The degree of similarity with the measured frequency characteristic as a model of the partial discharge is obtained, and when the similarity of the highest similarity is within a predetermined range, the measured signal is a partial discharge signal. By judging that there is, and by estimating the distance between the measurement point and the partial discharge occurrence point from the transfer function that obtained the frequency characteristic with the highest similarity, even if the partial discharge occurrence point is far from the measurement point, noise and It is possible to automatically identify the partial discharge signal and perform highly accurate partial discharge measurement, and it is possible to estimate the distance between the measurement point and the partial discharge occurrence location.

[Brief description of the drawings]

FIG. 1 is a diagram showing frequency characteristics of noise and a partial discharge signal.

FIG. 2 is a diagram showing a configuration of a partial discharge measurement system according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a frequency characteristic of a partial discharge signal generated at a distant place;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 CV cable 12 Intermediate insulation connection part 12a Simulated pulse generator 12c Partial discharge detector 12b, 12b 'Foil electrode 13 Amplifier 14 Electro-optical converter 15 Optical fiber 16 Opto-electric converter 17 Preamplifier 18 Spectrum analyzer 19 Processor 20 Recording device

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiyuki Sato 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Inventor Toshiki Sakamoto 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa (56) References JP-A-6-66875 (JP, A) JP-A-3-175377 (JP, A) JP-A-5-119104 (JP, A) JP-A-5-240902 ( JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G01R 31/12

Claims (2)

(57) [Claims] 1. A partial discharge measurement method for a power cable line for measuring a partial discharge generated in an insulated connection portion or a power cable line on both sides of the insulated connection portion, wherein the signal measured at the insulated connection portion is a signal. A frequency characteristic A (f) of the intensity is obtained, and the obtained frequency characteristic A (f) is supplemented with a transfer function C (f) corresponding to the distance between the measurement point and the partial discharge occurrence point by the following equation.
A corrected frequency characteristic A '(f) is obtained , and A' (f) = A (f) / C (f) The corrected frequency characteristic A '(f) and a frequency which is a model of a partial discharge measured in advance Determining a degree of similarity with the characteristic, and determining that the measured signal is a partial discharge signal when the degree of similarity between the two is within a predetermined range. . 2. An insulated connection or an insulated connection.
Measuring partial discharges occurring in power cable lines on both sides
In the method for measuring partial discharge of a power cable line, a transfer function C (f) of signal propagation in the power cable line.
Measured for each distance, and measured at the above insulated connection.
Frequency characteristic A (f) of the signal strength
Therefore , the obtained frequency characteristic A (f) is corrected by the following equation from the transfer function C (f) to obtain the frequency characteristic A ′ at each distance.
(F) the sought, A 'and (f) = A (f) / C (f) each of the frequency characteristic is corrected by the transfer function, the degree of similarity between the frequency characteristic as a model for pre-measured partial discharge When the degree of similarity of the highest degree of similarity is within a predetermined range, it is determined that the measured signal is a partial discharge signal, and the frequency characteristic with the highest degree of similarity is obtained. A partial discharge measuring method, comprising estimating a distance between a measurement point and a partial discharge occurrence point from a transfer function C (f) .