JPH09233679A - Corona discharge detector in power installation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to analyze corona discharge without a stoppage in power, by detecting a position of noise generation and its conditions in corona discharge on the basis of a containing rate of a frequency factor that is twice the power supply frequency in strong and weak factors. SOLUTION: A direction of sound in discharge is discriminated by an acoustic direction detecting unit 10. An acoustic detecting unit 1 is turned to the direction of sound to receive the sound in discharge. The sound is amplified in a first stage amplifier 2, passed through a high-frequency passing filter 3 to remove noises, and amplified again in a second stage amplifier 4. After the sound signal without noises is rectified by a rectifier 5, the sound signal is subjected to envelope detection, and an analog signal as strong and weak factors of the sound is converted into a digital signal by an A/D converter 7. The digital signal is fed to a CPU 8, and fast Fourier transform is carried out to obtain a stable waveform with frequency twice the power-supply frequency. As a result, the generating position of corona discharge can be judged from the acoustic signal and the conditions can be detected, and the analysis can be carried out without a failure in power.

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 in a power facility in operation.

[0002]

2. Description of the Related Art Conventionally, as a device for detecting an abnormality such as insulation deterioration due to corona discharge in a power facility in operation, as disclosed in Japanese Patent Laid-Open No. 49-50969, for example, corona discharge is detected. A method of detecting only the corona discharge signal by detecting with a device and sampling the signal at the timing synchronized with the power supply, or JP-A-58-21173.
As disclosed in Japanese Patent Laid-Open Publication No. 2003-242242, a method is known in which 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 by the integrated amount.

[0003]

However, the prior arts of the above-mentioned JP-A-49-50969 and JP-A-58-21173 have the following problems, respectively. That is, FIG. 6 shows an example of detecting corona by the former technique of Japanese Patent Laid-Open No. 49-50969, and FIG. 7 shows an example of detecting noise other than corona discharge. In Fig. 6, (a) is the corona discharge signal detected by the corona detection element, (b) is the signal A after the low frequency noise is removed by the noise eliminator, and (c) is near the peak value in synchronization with the power supply. The rectangular wave B is 1, which is 1 in other sections and 0 in other sections, and (d) is a signal obtained by multiplying A and B. Then, when corona is detected by the corona detecting element, a high frequency signal appears in the signal obtained by multiplying A and B in the cycle of the rectangular wave B.

Further, in FIG. 7, (a) is a stationary noise signal detected by the corona detecting element, (b) is a signal C after the low frequency noise is removed by the noise removing section, and (c) is a power source synchronized. Then, a square wave D that becomes 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 is detected by the corona detection element,
In the signal obtained by multiplying C and D, a high frequency signal appears in the cycle of the rectangular wave D.

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

In the latter method of Japanese Patent Laid-Open No. 58-21173, all the devices of the system to which the grounding transformer is connected are to be detected, so the drawback that the object is limited to one point is solved. However, since the method of detecting corona discharge samples the signal at the constant phase timing generated from the commercial frequency power supply, the signal after sampling is a true corona discharge signal as in the previous method. Even if there is noise, which is constantly generated, the same appearance is exhibited, and therefore corona discharge cannot be determined. Particularly in a system including harmonics, harmonic noises are constantly superposed on the ground line, and it is difficult to detect a weak corona discharge signal.

By the way, the present applicant has proposed a corona discharge detecting device for electric power equipment in Japanese Patent Application No. 7-282078 as means for overcoming the above-mentioned drawbacks of the prior art and accurately detecting corona discharge. The contents are, in a device for detecting corona discharge of electric power equipment, a sound detection unit that detects a sound generated when the corona discharge occurs, and a high frequency component is extracted from a detection signal of the sound detection unit to remove ambient noise. The noise removal unit, the envelope detection of the signal after noise removal by rectification, and the strong and weak component extraction unit that extracts the thing of the period of twice the power supply frequency as the strong and weak component of the corona discharge sound, and the power supply frequency in the strong and weak components It is characterized by including a determination unit that determines whether the sound is a corona discharge sound from the size of the component, and to detect insulation deterioration in a switchboard in an uninterruptible state. This is a very effective means.

However, in the case of this Japanese Patent Application No. 7-282078, an electric maintenance worker, for example, obtained information on detecting the sound of corona discharge at a monitoring center and then went to the site to check the presence or absence of discharge. At this time, in order to confirm in which part the discharge is occurring and in what manner the discharge is occurring, it is inevitable to stop after turning off the power source.

[0009] For example, when the electric discharge occurs in a busbar device such as an insulator, it is necessary to take a power outage for the entire substation equipment, but when the electric discharge is caused by a creeping discharge such as a cable,
Only the applicable feeder should be cut off and dealt with. However, in the case of the above-mentioned Japanese Patent Application No. 7-282078, it is not possible to determine which one of the discharges, and therefore it is necessary to always take a power outage of the entire substation equipment to deal with it. Also, in the case of discharge that develops into arc discharge that occurs from overheating of the contact part, there is an urgent need to promptly deal with it, but discharge that occurs due to voids in the insulator, such as creeping discharge of a cable. In some cases, dielectric breakdown may not occur even if left for a relatively long time.

As described above, although the coping method differs depending on the site of discharge and its aspect, the above-mentioned Japanese Patent Application No.
In −282078, it is possible to detect discharge, but it is not possible to analyze the location and aspect of discharge, so it is necessary to promptly take a power outage for the entire substation equipment in the end. The present invention has been made in order to solve the above-mentioned problems of the conventional technology, and is a corona discharge detection device for electric power equipment capable of acoustically analyzing a discharge site and its aspect without interruption. The purpose is to provide.

[0011]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a sound detecting section in which a sound receiving section for detecting a sound generated when a corona discharge occurs is swingable, and the sound detecting section. The acoustic azimuth detecting section which is attached in the vicinity of the section to detect the direction of sound generation, the noise removing section which extracts high frequency components from the detection signal of the acoustic detecting section to remove ambient noise, and the signal after noise removal Envelope detection is performed by rectification, and the strength component extraction unit that extracts the strength component of the corona discharge sound, and the generation location of the corona discharge sound and its appearance are determined from the content ratio of twice the power supply frequency component in the strength component. It is characterized in that it is configured so as to be integrally portable.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described 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 designates a sound detection unit such as an ultrasonic microphone having a strong directivity for detecting sound due to corona discharge, the sound receiving unit of which can be swung freely. 2 is a first-stage amplifier, 3 is a high-pass filter with a cut-off frequency of 10 kHz, 4 is a second-stage amplifier, 5 is a rectifier, 6 is a low-pass filter with a cut-off frequency of 200 Hz, 7 is A
A / D converter, 8 is a central processing unit, and 9 is a display. Reference numeral 10 denotes an acoustic direction detection unit such as a pointer using a laser diode, which is attached in the vicinity of the acoustic detection unit 1 and indicates the direction of the acoustic due to the corona discharge to the display unit 11 by light or the like, so that the location where the discharge sound is generated is detected. It can be visually confirmed. These devices are integrally assembled to a size that is easy to carry and are configured so that an electric maintenance person can carry them to the site for measurement.

Next, the operation of the corona discharge detecting device of the present invention thus constructed will be described. First, the direction of discharge sound is confirmed by using the acoustic direction detector 10 and the acoustic detection is performed in that direction. With the part 1 facing, a discharge sound having a waveform as shown in FIG. 2 (a) is collected. The discharge sound sampled by the acoustic detector 1 is first amplified by the amplifier 2 in the first stage into a waveform as shown in FIG. 2 (b), passes through the high-pass filter 3 and is removed of noise. . After the noise is removed, it is amplified again by the second-stage amplifier 4. The signal at this time is shown in Fig. 2 (c). Here, to explain the function of noise removal in the high-pass filter 3, normally, the sound generated by corona discharge exists at a high frequency of 10 kHz or more over a wide frequency band, but most of the environmental noise of general transformer equipment is Since the frequency component is 10 kHz or less, only the corona sound can be easily extracted by the high pass filter 3.

Then, the noise-removed signal is rectified by the rectifier 5 into a waveform as shown in FIG. 2 (d), and then envelope detection is performed by the low-pass filter 6 to generate a discharge sound as shown in FIG. 2 (e). The strength component of is extracted. Further, the analog signal of the intensity component 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 analog signal after envelope detection using the A / D converter 7 is converted into a digital signal because the signal before envelope detection becomes a wide-range signal up to the ultrasonic region (about 40 kHz). On the other hand, the signal after 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 frequency component of the signal is displayed as a spectrum by (Fast Fourier Transform) processing, and the signal waveform is displayed so that the presence or absence of the phase transition of the signal can be visually confirmed. The processing contents of the central processing unit 8 will be specifically described below. First, FIG. 3 shows the waveform of the void discharge after envelope detection, and it can be seen that the waveform is stable at 120 Hz, which is a frequency component twice the power supply frequency (60 Hz).
Further, FIG. 4 shows the waveform of the insulator creeping discharge after envelope detection, and it can be seen that it is characteristic that the sound pressure is larger than that of the void discharge and the period thereof may be displaced.

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

[0018]

[Table 1]

In particular, paying attention to the volume of the discharge sound and the content rate of the double frequency component of the power supply frequency, it is understood that there is a relation as shown in FIG. Therefore, by storing the relationship of FIG. 5 in the central processing unit 8 in advance,
By the sound pressure of the generated discharge sound, it is possible to determine the aspect of the discharge, that is, spark discharge, insulator creeping discharge, or void discharge. By this, in the case of the insulator surface discharge, the treatment is performed as being due to the contamination / wetting of the insulator, and in the case of the void discharge, it can be dealt with by focusing on the cable or epoxy.

[0020]

As described above, according to the corona discharge detecting apparatus of the present invention, it is possible to discriminate the corona discharge occurrence site and its appearance detected by the sound, so that the operation of the substation equipment is stopped. Without it, it is possible to detect a ground fault / short circuit accident due to insulation deterioration at an early stage and prevent the accident from spreading.

[Brief description of drawings]

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

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 void discharge.

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

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

FIG. 6 is a characteristic diagram showing an example of detecting corona in a conventional example.

FIG. 7 is a characteristic diagram showing an example of detecting noise other than corona discharge in the conventional example.

[Explanation of symbols]

 1 Acoustic Detection Unit 2 1st Stage Amplifier 3 High Pass Filter (Noise Removing Unit) 4 2nd Stage Amplifier 5 Rectifier (Strength Component Extraction Unit) 6 Low Pass Filter (Strength Component Extraction Unit) 7 A / D Conversion Device 8 Central processing unit (judgment unit) 9 Display 10 Acoustic direction detection unit 11 Display

Claims (1)

[Claims] 1. A device for detecting corona discharge of electric power equipment, wherein a sound detecting part for detecting a sound generated when corona discharge occurs is swingable, and a sound detecting part is mounted in the vicinity of the sound detecting part. An acoustic azimuth detecting section for detecting the direction of sound generation, a noise removing section for extracting high frequency components from the detection signal of the acoustic detecting section to remove ambient noise, and an envelope detection by rectifying the signal after noise removal. Then, a strength component extraction unit that extracts the strength component of the corona discharge sound, and a determination unit that determines the generation location of the corona discharge sound and its appearance from the content ratio of the frequency component twice the power supply frequency in the strength component. A corona discharge detection device for electric power equipment, characterized in that it is configured so that it can be carried integrally.