JP3334780B2 - Corona discharge detector for power equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting an abnormality such as insulation deterioration due to corona discharge of an operating power facility.

[0002]

2. Description of the Related Art Conventionally, as an apparatus for detecting an abnormality such as insulation deterioration due to corona discharge of an operating power facility, as disclosed in, for example, Japanese Patent Application Laid-Open No. 49-50969, a corona discharge is detected. A method of detecting only a corona discharge signal by detecting a signal with an element and sampling a signal at a timing synchronized with a power supply, or a method disclosed in Japanese Patent Application Laid-Open No. 58-21173.
As disclosed in Japanese Patent Application Laid-Open Publication No. H11-163, there is known a method in which a corona discharge is detected from a ground line, a signal is sampled at a constant phase timing generated from a commercial frequency power supply, and the corona discharge is detected based on the integrated amount.

[0003]

However, the above-mentioned prior arts of JP-A-49-50969 and JP-A-58-21173 each have the following problems. That is, FIG. 6 shows an example in which a corona is detected by the former technique of JP-A-49-50969, and FIG. 7 shows an example in which noise other than corona discharge is detected. In FIG. 6, (a) shows a corona discharge signal detected by a corona detecting element, (b) shows a signal A after low-frequency noise has been removed by a noise removing unit, and (c) shows a signal near a peak value synchronized with a power supply. 1, a rectangular wave B having 0 in other sections, and (d) are signals obtained by multiplying A and B. When a corona is detected by the corona detecting element, a high-frequency signal appears at a cycle of a rectangular wave B in a signal obtained by multiplying A and B.

In FIG. 7, (a) shows a stationary noise signal detected by a corona detecting element, (b) shows a signal C after low-frequency noise has been removed by a noise removing section, and (c) shows a signal synchronized with a power supply. Square wave D, which is 1 near the peak value and 0 in other sections, (d)
Is a signal obtained by multiplying C and D. Then, when a noise signal that constantly occurs in the corona detecting element is detected,
In a signal obtained by multiplying C and D, a high-frequency signal appears at a period of the rectangular wave D.

[0005] As shown in these figures, whether the signal is a true corona discharge signal or a stationary noise,
Since the signal after sampling has exactly the same appearance, it is difficult to determine that the signal is a corona discharge even if a corona discharge signal is detected. Therefore, there is a problem that it cannot be used in an environment where stationary noise is generated (in a power supply system such as a slip ring noise of an AC motor). In addition, since only one object is to be detected for corona detection, for example, when monitoring an abnormality in the entire substation, the detection device must be grounded for each device, which is economically problematic. was there.

The method disclosed in Japanese Patent Application Laid-Open No. 58-21173 solves the disadvantage that only one device can be detected because all devices in the system to which the grounding transformer is connected are to be detected. However, since the method of detecting corona discharge samples the signal at a constant phase timing generated from the commercial frequency power supply, the signal after sampling is a true corona discharge signal, as in the method described above. Even if the noise is constantly generated, the corona discharge cannot be determined because the noise looks exactly the same. Particularly in a system including harmonics, the harmonic noise is constantly superimposed on the ground line, and it is difficult to detect a weak corona discharge signal.

By the way, the present applicant has already proposed a corona discharge detecting device for electric power equipment in Japanese Patent Application No. 7-282078 as a means for overcoming the above-mentioned disadvantages of the prior art and accurately detecting corona discharge. The contents are as follows. In a device for detecting corona discharge of electric power equipment, a sound detection unit that detects sound generated when corona discharge occurs, and a high-frequency component is extracted from a detection signal of the sound detection unit to remove peripheral noise. A noise removing unit, a strong component extracting unit that performs envelope detection by rectifying the signal after noise removal, and extracts a component having a period twice as long as the power frequency as a strong component of the corona discharge sound, and a power frequency within the strong component. A determination unit that determines that the sound is a corona discharge sound from the magnitude of the component, characterized in that it is characterized by the fact that insulation deterioration in the switchboard is detected in an uninterrupted state. This is a very effective means.

However, in the case of Japanese Patent Application No. 7-282078, after an electrical maintenance person obtains information on the detection of corona discharge sound at a monitoring center, for example, he or she goes to the site to check for the presence or absence of discharge. At that time, in order to confirm where the discharge is occurring and in what manner the discharge is occurring, it is necessary to confirm after stopping the power source.

For example, when a discharge occurs in a bus device such as an insulator, it is necessary to take measures by stopping the entire substation equipment, but when the discharge is caused by a creeping discharge of a cable or the like,
Only the corresponding feeder needs to be dealt with after a power outage. However, in the case of the aforementioned Japanese Patent Application No. 7-282078, it is not possible to determine which type of discharge, and it is necessary to always take measures by stopping the power of the entire substation facility. In addition, in the case of a discharge that develops into an arc discharge that occurs due to overheating of the contact portion, there is an urgent need to deal with the discharge immediately, but a discharge that is caused by voids in the insulator, such as a creeping discharge of a cable. In some cases, the dielectric breakdown does not occur even if left for a relatively long time.

As described above, despite the fact that the countermeasures are different depending on the location of the discharge and the aspect thereof, the above-mentioned Japanese Patent Application No. Hei.
In -282078, although it is possible to detect a discharge, it is not possible to analyze the location and appearance of the discharge, and eventually, it is necessary to take measures immediately after a blackout of the entire substation equipment. SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art as described above, and is a corona discharge detection device for electric power equipment capable of analyzing a discharge site and its appearance by sound without interruption. The purpose is to provide.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a sound detecting section in which a sound receiving section for detecting sound generated when corona discharge occurs is swingable, A sound direction detecting unit attached near the unit for detecting a sound generation direction, a noise removing unit for extracting high frequency components from a detection signal of the sound detecting unit to remove peripheral noise, and a signal after noise removal. The corona discharge sparks based on the envelope detection by rectification and the strong and weak component extraction unit that extracts the strong and weak components of the corona discharge sound, and the content ratio of the frequency component twice the power supply frequency in the strong and weak components and the sound pressure of the discharge sound. Discharge
It is characterized in that it is configured such that a determination unit for determining whether the surface discharge is an insulator surface discharge or a void discharge can be integrally carried.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a corona discharge detection device according to the present invention, and FIG. 2 is a characteristic diagram showing output waveforms at respective elements of the corona discharge detection device.

In these figures, reference numeral 1 denotes a sound detection unit such as an ultrasonic microphone having a high directivity for detecting sound due to corona discharge, and its sound receiving unit is swingable. 2 is a first-stage amplifier, 3 is a high-pass filter having a cutoff frequency of, for example, 10 kHz, 4 is a second-stage amplifier, 5 is a rectifier, 6 is a low-pass filter having a cutoff frequency of, for example, 200 Hz, and 7 is A
A / D converter, 8 is a central processing unit, and 9 is a display. Reference numeral 10 denotes an acoustic azimuth detecting unit such as a pointer using a laser diode, which is attached near the acoustic detecting unit 1 and indicates the direction of the sound due to corona discharge with light or the like, thereby visually confirming the location where the discharge sound is generated. be able to. These devices are integrally assembled to easily transportable dimensions, and are configured so that electrical maintenance personnel can carry them to the site and measure them.

[0014] Next, the operation of the corona discharge detector of the present invention configured as above, first, Leh
The direction of discharge sound generation is confirmed by pointing to the direction using the sound direction detection unit 10 such as a pointer , and the sound detection unit 1 is pointed in that direction, and the discharge sound having a waveform as shown in FIG. Collect. The discharge sound collected by the sound detection unit 1 is first amplified by the first-stage amplifier 2 into a waveform as shown in FIG. 2 (b) and passed through the high-pass filter 3 to remove noise. . After the noise is removed, the signal is amplified again by the second-stage amplifier 4. The signal at this time is shown in FIG. Here, the function of removing noise in the high-pass filter 3 will be described. Usually, the sound generated by corona discharge is 10 kHz.
Although the above-mentioned high frequencies exist over a wide frequency band, most of the environmental sounds of general substation equipment have frequency components of 10 kHz or less, so that only the corona sound can be easily extracted by the high-pass filter 3. .

The signal from which noise has been removed is rectified by the rectifier 5 into a waveform as shown in FIG. 2 (d), and then subjected to envelope detection by the low-pass filter 6 to produce a discharge sound as shown in FIG. 2 (e). Extract the strong and weak components of. Further, the analog signal of the strong and weak components of the discharge sound is converted into a digital signal by the A / D converter 7 and guided to the central processing unit 8. Here, the reason why the analog signal after the envelope detection using the A / D converter 7 is converted into a digital signal is that the signal before the envelope detection becomes a signal in a wide range up to the ultrasonic range (about 40 kHz). On the other hand, the signal after the envelope detection is several times the frequency of the power supply voltage (about 200 Hz), the sampling rate can be set low, and the load on the central processing unit 8 can be reduced.

Further, in the central processing unit 8, the FFT
The spectrum of the frequency component of the signal is displayed by (Fast Fourier Transform) processing, and the signal waveform is displayed so that the presence or absence of the transition of the phase of the signal can be visually confirmed. Hereinafter, the processing contents of the central processing unit 8 will be specifically described. First, FIG. 3 shows the waveform of the void discharge after the envelope detection, and it can be seen that the waveform is a stable waveform of 120 Hz, which is twice the frequency component of the power supply frequency (60 Hz).
FIG. 4 shows the waveform of the surface discharge of the insulator after the envelope detection. It can be seen that the sound pressure is larger than that of the void discharge, and the period thereof may be transposed.

On the other hand, when the frequency component ratio of the void discharge and the surface discharge of the insulator was examined, it was found that the ratio was as shown in Table 1 below.

[0018]

[Table 1]

In particular, when attention is paid to the magnitude of the discharge sound and the content of the frequency component twice as high as the power supply frequency, it can be seen that there is a relationship approximately as shown in FIG. Therefore, by storing the relationship of FIG. 5 in the central processing unit 8 in advance,
Based on the sound pressure of the generated discharge sound, it is possible to determine whether the discharge is spark discharge, insulator surface discharge, or void discharge. Thus, in the case of the surface discharge of the insulator, a measure is taken as being caused by the soiling and wetting of the insulator, and in the case of the void discharge, it is possible to deal with the problem by focusing on the cable or the epoxy.

[0020]

As described above, according to the corona discharge detecting device of the present invention, the location of the corona discharge detected by sound and its appearance can be determined, and the operation of the substation equipment is stopped. Without detecting an earth fault or short circuit accident due to insulation deterioration at an early stage, it is possible to prevent the accident from spreading.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a corona discharge detection device according to the present invention.

FIGS. 2A to 2E are characteristic diagrams showing output waveforms at respective elements of the corona discharge detection device.

FIG. 3 is a characteristic diagram of a waveform in a void discharge.

FIG. 4 is a characteristic diagram of a waveform in an insulator surface discharge.

FIG. 5 is a characteristic diagram showing a relationship between a sound pressure of a discharge sound and a content of a frequency component twice as high as a power supply frequency.

FIG. 6 is a characteristic diagram showing an example in which a corona is detected in a conventional example.

FIG. 7 is a characteristic diagram showing an example in which noise other than corona discharge is detected in a conventional example.

[Explanation of symbols]

Reference Signs List 1 sound detection unit 2 first-stage amplifier 3 high-pass filter (noise removal unit) 4 second-stage amplifier 5 rectifier (strong and weak component extraction unit) 6 low-pass filter (strong and weak component extraction unit) 7 A / D conversion 8 Central processing unit (judgment unit) 9 Display 10 Sound direction detection unit

Claims (1)

(57) [Claims] 1. An apparatus for detecting corona discharge in an electric power facility, comprising: a sound detector for detecting a sound generated when the corona discharge occurs; a sound detector that is swingable; and a sound detector mounted near the sound detector. A sound azimuth detecting unit for detecting a direction in which the sound is generated, a noise removing unit for extracting a high-frequency component from a detection signal of the sound detecting unit to remove peripheral noise, and an envelope detection by rectifying the signal after noise removal. Then, the corona discharge is spark discharge or insulator surface discharge based on the strength component extraction unit that extracts the strength component of the corona discharge sound, and the sound frequency of the discharge sound and the content ratio of the frequency component twice the power supply frequency in the strength component. Oh
A corona discharge detection device for electric power equipment, wherein a determination unit for determining whether the discharge is void discharge or not is configured to be integrally portable.