JP2000002743A - Insulation deterioration diagnostic method for high- voltage equipment such as high-voltage overhead cable branch connecting body for power distribution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely diagnose partial discharge deterioration for a high-voltage equipment such as a high-voltage overhead cable branch connecting body for power distribution, and to prevent service interruption caused by dielectric breakdown. SOLUTION: A high frequency current signal detected by an isolation current transformer 1 attached to a lead-in cable 6 branched by a connecting body 5 is amplified by an amplifier 2 to be measured thereafter by a spectrum analyzer 3, and stored in a memory inside a computer 4. The wave form pattern of the high frequency current signal stored in the memory and a frequency spectrum are investigated to diagnose the degree of partial discharge in the connecting body 5 (a degree of dielectric breakdown).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for diagnosing insulation deterioration of a high-voltage device such as a branch connector of a high-voltage overhead cable for power distribution (hereinafter referred to as a "connector"). The present invention relates to a method for diagnosing insulation deterioration of a high-voltage device such as a distribution high-voltage overhead cable branch connector for detecting a high-frequency current pulse propagating through a cable (hereinafter referred to as a “recessed cable”) and diagnosing the degree of insulation deterioration.

[0002]

2. Description of the Related Art In a branch connection of a high-voltage overhead cable for distribution, as the insulation deterioration progresses, a partial discharge occurs at the insulation deterioration part. Therefore, the diagnosis of insulation deterioration in the branch connection of the high-voltage overhead cable for distribution has been made by detecting the occurrence state of the partial discharge.

[0003] In a conventional method for diagnosing insulation deterioration of a high-voltage aerial cable branch connector for distribution, a partial discharge signal is indirectly captured by observing a potential variation on the surface of a housing using a sensor capacitively coupled to the housing. I was In this case, when a partial discharge occurs, the distribution of the potential fluctuation spectrum of the partial discharge signal is observed in a wide frequency range, and the waveform on the time axis (hereinafter simply referred to as a waveform) is also detected periodically (at intervals of 10 ms). Become so. By detecting the potential fluctuation spectrum, the state of occurrence of partial discharge is indirectly grasped, and the state of occurrence of partial discharge is estimated by analyzing the frequency distribution thereof, thereby diagnosing the state of insulation deterioration.

[0004] FIG. 3 shows a measurement result of the fluctuation of the housing potential.
FIG. 3A shows a frequency spectrum measurement result of a connection body having a sound state, and FIG. 3B shows a frequency spectrum measurement result of a connection body in which partial discharge deterioration is progressing.
(C) shows the measurement result of the waveform of the connection body having a healthy shape, and FIG. 3 (d) shows the measurement result of the waveform of the connection body in which partial discharge deterioration is progressing.

As can be seen from FIG. 3, as the partial discharge deterioration of the connector progresses, both the frequency spectrum and the waveform in the time domain become larger.

As described above, in the conventional method for diagnosing insulation deterioration of high-voltage equipment such as a high-voltage overhead cable branch connection for power distribution, a potential change signal induced on the surface of a casing when a partial discharge occurs is detected. By indirectly grasping the partial discharge and examining the frequency distribution thereof, the occurrence state of the partial discharge was estimated, and the state of insulation deterioration was diagnosed.

[0007]

However, according to the conventional method for diagnosing insulation deterioration of high-voltage equipment such as a high-voltage overhead cable branch connection for distribution, environmental noise is large with respect to a potential fluctuation signal generated by partial discharge. In such a case, it was difficult to accurately detect the partial discharge on site.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the S / N ratio between a partial discharge signal and environmental noise to accurately diagnose partial discharge deterioration and prevent a power failure due to dielectric breakdown. Provided is a method for diagnosing insulation deterioration of a high-voltage device such as a cable branch connector.

[0009]

According to the present invention, a current transformer is mounted on a cable connected to a high-voltage device, such as a distribution high-voltage overhead cable branch connector, in order to achieve the above object. Insulation degradation of high-voltage equipment such as a high-voltage overhead cable branch connection for distribution, characterized by detecting a high-frequency current signal and examining the waveform pattern and frequency spectrum of the high-frequency current signal to diagnose the degree of insulation deterioration of high-voltage equipment. Provide a diagnostic method.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for diagnosing insulation deterioration of a high-voltage device such as a high-voltage overhead cable branch connector for power distribution according to the present invention will be described in detail below.

FIG. 1 shows a method of observing a high-frequency current signal in a method for diagnosing deterioration of insulation of a high-voltage device such as a branch connector of a high-voltage overhead cable for distribution according to the present invention. The high-frequency current signal detected by the separate type current transformer (CT) 1 attached to the transformer lead-in cable 6 branched by the connecting body 5 of the distribution high-voltage overhead cable 7 is amplified by the amplifier 2. Are measured by the spectrum analyzer 3 and stored in a memory (not shown) in the computer 4. In the computer 4, the waveform pattern and frequency spectrum of the high-frequency current signal stored in the memory are checked,
The degree of the partial discharge of the connector 5 (the degree of insulation deterioration) is diagnosed.

Using the diagnostic criteria shown in Table 1 with respect to the frequency spectrum and the waveform result of the detected high-frequency current signal, the insulation state of the connector 3 can be diagnosed.

[0013]

[Table 1]

FIG. 2 shows the measurement results of the high-frequency current of the drop cable. FIG. 2A shows a frequency spectrum measurement result of a healthy body-like connection, and FIG. 2B shows a frequency spectrum measurement result of a connection body in which partial discharge deterioration is progressing. c) shows the measurement result of the waveform of the connection body having a sound state, and FIG. 2D shows the measurement result of the waveform of the connection body in which partial discharge deterioration is progressing.

As the partial discharge deterioration of the connector 5 progresses, both the frequency spectrum and the waveform become larger. In particular, when partial discharge is occurring,
A large frequency spectrum is observed in the bands of 6 MHz and 6 to 10 MHz, and a group of pulses is generated at intervals of 10 ms in the waveform. On the other hand, general environmental noise has a small spectrum in the band of 2 to 6 MHz and 6 to 10 MHz, and no pulse waveform is observed. Further, the S / N ratio between the partial discharge signal and the environmental noise becomes excellent in the partial discharge measurement method for detecting the high-frequency current of the drop cable 6.

Therefore, by observing the frequency spectrum distribution and the pulse waveform of the high-frequency current signal of the dropping cable 6 branched by the connecting body 5 in the 10 MHz band, the sound state and the deteriorated state of the connecting body 5 can be accurately diagnosed. be able to.

Although the present invention has been described with reference to one embodiment, the high-voltage equipment is not limited to a high-voltage overhead cable branch connection for distribution, but may be applied to other high-voltage equipment such as a transformer and a switch. Can be.

[0018]

As described above, according to the method for diagnosing insulation deterioration of a high-voltage device such as a branch connector of a high-voltage overhead cable for power distribution according to the present invention, a current transformer is attached to a service cable and a high-frequency current pulse is captured. Since the discharge is measured indirectly, the magnitude of the environmental noise with respect to the partial discharge is smaller than that of the conventional method of observing the potential fluctuation, so that a diagnosis of a smaller partial discharge can be performed.

Furthermore, by using the method for diagnosing insulation deterioration of the present invention for periodic inspections and the like, a sound state and an insulation deterioration state can be clearly determined in a live state, so that a power failure due to insulation breakdown of high-voltage equipment can be anticipated. Can now be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for observing a high-frequency current signal in a method for diagnosing insulation deterioration of a high-voltage device according to the present invention.

FIG. 2 is a diagram showing a measurement result of a high-frequency current of a drop cable.

FIG. 3 is a diagram showing a measurement result of a housing potential fluctuation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Current transformer 2 Amplifier 3 Spectrum analyzer 4 Computer 5 Connection body 6 Drop-in cable 7 High-voltage cable for power distribution

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takuji Chindo 4-1 Egasakicho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Within the Tokyo Electric Power Company (72) Inventor Shin Kataoka 5 Hidakacho, Hitachi City, Ibaraki Prefecture 1-1-1 Hitachi Power Systems Co., Ltd. Power System Research Laboratory (72) Inventor Kazuo Kotani 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture F-Term Power System Research Laboratory Hitachi Cable, Ltd. 2G015 AA27 BA10 CA01 CA20

Claims (3)

[Claims] 1. A current transformer is attached to a cable connected to a high-voltage device such as a distribution high-voltage overhead cable branch connector, a high-frequency current signal is detected by the current transformer, and a waveform pattern and frequency of the high-frequency current signal are detected. A method for diagnosing insulation deterioration of a high-voltage device such as a distribution high-voltage overhead cable branch connection, comprising examining a spectrum to diagnose a degree of insulation deterioration of the high-voltage device. 2. The step of diagnosing the degree of insulation deterioration of the high-voltage device includes the step of determining the frequency and magnitude of the high-frequency current signal within a predetermined time and the frequency spectrum distribution of the high-frequency current signal in a predetermined frequency range. 2. The method for diagnosing insulation deterioration of a high-voltage device such as a high-voltage overhead cable branch connection for power distribution according to claim 1, wherein the deterioration diagnosis is performed based on the deterioration diagnosis. 3. The step of mounting the current transformer, wherein the current transformer is mounted on a transformer branch drop cable connected to a high voltage overhead cable branch connection for power distribution as the high voltage device. A method for diagnosing insulation deterioration of high-voltage equipment, such as the distribution high-voltage overhead cable branch connection described in the above.