JP2001305178A - Pattern recognition type partial discharge detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily detect partial discharge by separating a signal of a noise component from an ultrasonic wave signal gathered by a microphone and transmitting only a signal due to the partial discharge to a display part. SOLUTION: A detecting device 1 is constituted by arranging an ultrasonic wave sensor 2 which collects an ultrasonic wave, a band-pass filter 3, and a detecting circuit 4 and transmits the output of an additional filter circuit 5 which passes only a frequency twice as high as the commercial power frequency to a display device to display it. Then frequencies other than a specific frequency are removed to transmit only information on a vibration wave due to the partial discharge to the display device 6, so that the discharge can easily be decided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a partial discharge detector in power transmission and distribution facilities including high-voltage electrical facilities,
The present invention relates to a device for detecting electromagnetic waves, sound waves, ultrasonic waves, and the like generated from a discharge unit.

[0002]

2. Description of the Related Art In general, power transmission and distribution equipment including high-voltage electrical equipment is provided with a private power receiving equipment on a high-voltage distribution line from a supply substation (distribution substation), and supplies power to each demand part of the private power receiving equipment. Make up the route. In a general factory or the like, a facility is provided that branches from a high-voltage distribution line from a distribution substation to a private power receiving facility and connects the same, and supplies low-voltage power to a motor and the like through a transformer. In power transmission and distribution equipment including the high-voltage electrical equipment, partial discharge may occur in insulators and equipment due to deterioration and the like in electrical equipment and the like provided in cables and cubicles. When the discharge occurs, there is a problem that the insulation performance of the equipment in operation or the insulation of the cable is reduced or lost, which leads to a serious dielectric breakdown accident.

Therefore, in the above-mentioned power transmission and distribution equipment,
Detecting partial discharge in the early stage that does not lead to a major accident,
It is important to take measures in advance to prevent equipment degradation and dielectric breakdown. For that purpose, at present, using a directional device such as a sound-collecting microphone, a Yagi-Uda antenna, etc., a cable stretched between telephone poles, a device installed on a telephone pole, and a power receiving side are provided. 2. Description of the Related Art Electromagnetic waves, ultrasonic waves, and the like generated by partial discharge are captured for devices such as transformers, and their detection information is analyzed. In addition, by using a sound collector having no directivity, it is also performed to detect the occurrence of discharge in a device or the like disposed inside a closed box such as a cubicle.

[0004]

BACKGROUND OF THE INVENTION Partial discharges in power transmission and distribution equipment are intended for the deterioration or destruction of insulators caused by void discharges, creeping discharges, etc., which are called corona discharges. As described above, a relatively weak discharge is generated in the gap, and if the discharge continues, the insulator around the gap is gradually eroded or dendritic deterioration holes (trees) are generated. Leads to destruction. Further, similar deterioration or destruction occurs due to creeping discharge generated from the edge of the electrode or the like. The partial discharge is a local discharge that occurs at a place where a potential gradient is large, and is partially generated in an insulator when a voltage is applied to an insulating configuration system having a certain electrode arrangement and the applied voltage is increased. This indicates discharge, and partial discharge does not cause full-path breakdown. However, when such partial discharge occurs, the ionization effect increases, and when the concentration of current in that part and the density of space charge increase, light and sound are generated, and furthermore, erosion of the insulator occurs, resulting in insulation. Since the body deteriorates, it is necessary to detect the partial discharge at an early stage and take a countermeasure.

[0005] In recent years, electric devices and cables have become higher in voltage and smaller in size, and the electric field applied to the insulator has increased. As a result, there is a remarkable tendency that partial discharge occurs easily in contact with the inside or surface of the insulator. . Generally, when a partial discharge occurs, a sound wave having a wide frequency band from the audible range to the ultrasonic band is generated, and at the same time, an electromagnetic wave having a wide frequency band from several tens of kHz to several hundred MHz is generated. These ultrasonic waves and electromagnetic waves are radiated over a wide area without the outer case or shield of the equipment.Partial discharges generated on the conductor or insulator surface of the overhead cable are And electromagnetic waves can be detected.

For example, in a test circuit having a configuration as shown in FIG. 14, when a commercial frequency AC voltage is applied from the applied power supply 8 to the DUT 9 and a partial discharge occurs in the DUT 9, FIG. A current flows as shown in the charging current waveform example. In the waveform of FIG. 15, the positive potential is low in the waveform portion, so that partial discharge does not occur, but as the potential gradually increases, partial discharge occurs in the portion. Further, the partial discharge stops in the portion because the potential is lowered, but the same phenomenon occurs in the negative portion of the waveform. As described above, the ultrasonic waves generated by the partial discharge have a specific pattern in which the generation and the stop are repeated twice per one cycle of the AC waveform. The electromagnetic wave generated by the partial discharge also has the same generation pattern as that of the ultrasonic wave, and is generated in a cycle twice the AC applied voltage as shown in the graph of FIG.

In addition to the generation of the ultrasonic waves shown in FIG. 16, when it is intended to detect the partial discharge using the ultrasonic waves, the ultrasonic waves generated by the partial discharges and the ultrasonic waves due to mechanical vibration and the like are also generated. Is detected. For example, as shown in FIG. 17, the ultrasonic waves generated by the vibration of the machine or the wind hitting the cable are detected as having continuous and random generation without a specific pattern. It is also characterized in that electromagnetic waves for telecommunications and the like often do not have a specific pattern.

Conventionally, a partial discharge detection device has been used to detect the ultrasonic waves and the like to specify a partial discharge location. For example, an ultrasonic detection device, an electromagnetic wave detection method, and a charge waveform are used for diagnosis. Various types of devices are commercially available. In the ultrasonic detection device, the electromagnetic wave generated from the partial discharge location, the sound wave, out of the ultrasonic wave, the radiant energy is large, the directivity is strong, catching the ultrasonic wave which is easy to handle as a signal It is used to locate and detect a location from a distance. Then, the ultrasonic waves generated from the discharge location are focused by a directional sound collector,
Detected by an ultrasonic sensor (reception frequency is often 40 kHz), the information is converted into an electric quantity and displayed on a meter, etc.
The technician makes the determination based on the display.

In the electromagnetic wave detection system, an electromagnetic wave generated from a discharge location is captured by an antenna, converted into an electric charge, and displayed on a meter or the like, similarly to the ultrasonic system. In this method, the receiving frequency ranges from about 100 MHz to several hundred M
There are many Hz. Note that the selection of the frequency targets a frequency other than the various mobile communication bands and the broadcast frequency band. In the diagnosis method based on the charging current waveform, a sine-wave alternating current is applied to a high-voltage cable or the like, and when a partial discharge occurs, the above-described electric vibration is generated.

[0010]

The above-mentioned various partial discharge detection systems have the same disadvantages in any of the ultrasonic wave, electromagnetic wave and charge current detection systems, but the following devices are most frequently used. Is an ultrasonic partial discharge detection device. However, since the ultrasonic system uses a sound collecting microphone, in addition to an ultrasonic wave having a specific pattern caused by a partial discharge such as an electromagnetic wave or an ultrasonic wave, a radio wave for telecommunications is used. It also catches ultrasonic waves that include noise such as mechanical vibrations and wind noise. Therefore, conventionally, an experienced technician selects and detects only vibration information due to discharge from various types of vibration sounds. However, selecting and judging only information due to partial discharge from various types of detection information has a problem that many individual differences occur and an inaccurate insulation diagnosis is performed. Further, the above-described detection method based on experience alone has a problem that it is difficult to catch information due to partial discharge, particularly for a cable stretched outdoors in a windy place.

The present invention solves the above-described problem of detecting a discharge by a conventional sound-collecting microphone or the like. A discharge detector is provided with means for separating only information due to a partial discharge. It is an object of the present invention to provide a device that can accurately detect information to be performed.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a pattern recognition type partial discharge detector.
A sensor for detecting ultrasonic waves, electromagnetic waves or charging current, a filter circuit for selectively passing and amplifying signals from the sensor, and a rectifying signal transmitted from the filter circuit to form and output an envelope A detection circuit is provided, and a filter circuit for passing only a selected specific frequency from a signal output from the detection circuit, amplifying the signal, and outputting the amplified signal is provided. According to a second aspect of the present invention, there is provided a filter circuit which passes only a specific frequency selected from a signal output from the detection circuit, and amplifies and outputs the signal. Is provided.

According to a third aspect of the present invention, there is provided a detection circuit for rectifying a signal transmitted from a filter circuit to form and output an envelope, and outputting an output value of the detection circuit to a reference voltage value output from a reference voltage circuit. And a filter circuit that allows only a specific frequency selected from the output information from the comparison circuit to pass, amplifies and outputs the result.

According to a fourth aspect of the present invention, a DC component of an output value of a detection circuit is cut, and only a specific frequency selected from a capacitor to be amplified and output and information output from the capacitor is passed to amplify. And a filter circuit for outputting the output.

With the above-described configuration, in the detection device of the present invention, the noise other than the discharge signal such as the mechanical vibration and the air vibration can be obtained by the simple signal processing from the ultrasonic signal collected by the ultrasonic sensor. , The discharge can be accurately detected, and the inspection accuracy of the discharge can be improved. Also, since the circuit used for the detection device can be configured as a simple one and the signal processing is easy,
It can be easily incorporated into a conventional device, can be used in the same manner as a conventional device, and can detect a minute discharge with high accuracy by increasing discharge detection sensitivity.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration and operation of the device of the present invention will be described with reference to the illustrated example. The detection device 1 shown in FIG. 1 passes only a specific frequency selected from an ultrasonic sensor 2, a band-pass filter 3, a detection circuit 4, and a signal output from the detection circuit 4. An additional filter circuit 5 as a filter circuit for amplifying and outputting the amplified signal is sequentially arranged, and the signal obtained by the additional filter circuit 5 is displayed on the display device 6. The ultrasonic sensor 2 of the detection device 1 is a device such as a microphone that selectively detects ultrasonic vibration output from a target object such as an overhead cable and converts the ultrasonic vibration into an electric signal. A vibrator or the like is used. The band-pass filter 3 is a band-pass filter for an ultrasonic signal. When the frequency selectivity obtained by the ultrasonic sensor 2 is further increased, a specific frequency is selectively passed and, at the same time, amplified to a required size. The frequency passing through the band-pass filter 3 is set to be the same as the detection frequency of the ultrasonic sensor 2.

The detection circuit 4 rectifies and smoothes the signal (AM detection), removes frequency components higher than the audio frequency component, forms an envelope, and outputs the envelope as an audio frequency. The ultrasonic sensor 2, the band-pass filter 3, and the detection circuit 4
And a mechanism for processing a received signal is used in a conventional partial discharge detection device. In the present invention, an additional filter circuit 5 described below is newly added. It is a feature. The additional filter circuit 5
Is a circuit newly provided in the present invention, which is 100 Hz at a power frequency of 50 Hz and 120 H at a power frequency of 60 Hz.
Let z be a bandpass filter. By providing the additional filter circuit 5 in addition, a selectively detected partial discharge signal can be transmitted to the display device 6 as an output signal, and the output level of the display device 6 causes the meter needle to swing. And so on, and can be displayed more accurately.

In the detection device 1, the signal a processed and output by the band-pass filter 3 is shown in FIG.
The signal has an intermittent waveform as shown in FIG. Therefore, the signal b processed by the detection circuit 4 is shown in FIG.
Is output as an intermittent signal having a period twice as long as the power supply frequency. At this stage, the ultrasonic components are removed and converted to audio frequencies. The frequency component shown in FIG. 2B has the highest energy level at a frequency twice the power supply frequency and passes through a band-pass filter having a pass frequency twice the power supply frequency of the additional filter circuit 5. Thus, a large output having a waveform as shown in FIG. 2C can be obtained, and the information c can be transmitted to the display device 6 and displayed. Therefore, by checking the display on the display device 6, it is possible to easily know the occurrence of the partial discharge without depending on the skill level of the engineer.

FIG. 2 illustrates the case of a signal caused by the power supply frequency.
In addition to the required frequency, noise such as wind noise and mechanical vibration is simultaneously detected. When the information of the noise component is processed through the band pass filter 3, it is output as shown in FIG. 3A, but is obtained as a signal substantially the same as the signal of FIG. FIG. 3 (a)
Is processed through the detection circuit 4 into a waveform shown in FIG. 3B, which is output as a random signal having no specific pattern. Since the frequency component of this waveform is a random waveform, In particular, energy is not distributed over a wide band and the energy level at a specific frequency is not high. Therefore, when the signal shown in FIG. 3B is passed through an additional filter circuit 5 having a pass frequency twice as high as the power supply frequency, the waveform shown in FIG. 3C is obtained. The information is transmitted from the circuit 5 to the display device 6. Therefore, even if the noise is received by the ultrasonic sensor 2, a signal of the noise is not displayed on the display device 6 in addition to the signal of the occurrence of the discharge, so that the information of the occurrence of the discharge is affected. Never.

When the signal received by the ultrasonic sensor 2 of the detection device 1 has a very small noise component or a low noise level, the signal output from the band-pass filter 3 is as shown in FIG. As shown, a state in which a component having a vibration frequency twice as high as the power supply frequency is output strongly. That is, the signal a from the location where the partial discharge occurs is output as a large value, and the other signals b are obtained as very small values. Since the difference between the peak portion a and the dip portion b of the output waveform output from the detection circuit 4 is large as shown in FIG. 5, the partial discharge can be easily detected by passing through the additional filter circuit 5. Can be.

When the level of the noise is low, it can be processed by the detection device 1 as described above, but when the noise is very strong, as shown in the graph of FIG. The signal b of the noise component is obtained as a larger value than the signal a from the location where the partial discharge occurs.
Also, the output waveform output from the detection circuit 4 has a small difference between the peak portion a and the dip portion b as shown in FIG. This makes it difficult to detect partial discharge. Therefore, for a state where the noise component appears strongly,
The use of the detection device 10 as shown in FIG.

In the detection device 10 shown in FIG.
The reference voltage circuit 14 and the comparator 15 are arranged before the additional filter circuit 16 with respect to the ultrasonic sensor 11, the band-pass filter 12, and the detection circuit 13. The reference voltage circuit 14 detects 1/2 of the level difference between the noise component b of the signal waveform and the peak component a of the waveform due to partial discharge with respect to the signal output from the detection circuit 13 as shown in FIG. I do. Then, the reference voltage Vs =
A tracking voltage is automatically generated so as to be (a + b) / 2. The reference voltage Vs is determined by averaging a certain time or a certain cycle. The signal processing is performed by A
A method of converting a digital signal by a / D converter and a method of performing analog processing can be used. In the comparator 15 to which the signals from the reference voltage circuit 14 and the detection circuit 13 are input, when the input voltage input to the (+) terminal becomes higher than the reference voltage input from the (-) terminal, the output voltage becomes higher. This is a circuit that goes from minus to plus (some circuits have reverse polarity).

In the comparator 15, FIG.
As shown in (2), the input signal is compared with a reference voltage, and a pulse such as an output voltage waveform is generated every time the reference voltage line is crossed. Although the pulse width becomes non-uniform, the pulse generation cycle is の of the power supply frequency, and the energy level is the highest at twice the power supply frequency. Then, the presence or absence of discharge can be detected by passing the output signal through an additional filter circuit 16 having a pass frequency twice as high as the power supply frequency, and the output signal of the additional filter circuit 16 is directed to the display device 17. And output such as the output waveform of FIG. 10 can be displayed on a display or a meter. When noise such as mechanical vibration is received, the cycle of the output pulse of the comparator 15 becomes random and does not have a fixed cycle, so that energy is distributed over a wide band and the output signal of the additional filter circuit 16 is output. Is reduced, it is possible to determine that the signal is due to discharge.

In addition to the detection device shown in FIGS. 1 and 8, another detection device capable of separating noise satisfactorily is shown in FIG.
An apparatus as shown in FIG. 11 includes a capacitor 24 such as a coupling capacitor between an ultrasonic sensor 21, a bandpass filter 22 and a detection circuit 23, and an additional filter circuit 25. The capacitor 24 cuts the DC component of the output signal of the detection circuit 23 and increases the amplification of the additional filter circuit 25 connected to the output side.

The signal d output from the detection circuit 23
However, as shown in FIG. 12, a problem such as circuit saturation occurs due to the inclusion of a DC component, and it is difficult to increase the degree of amplification of the additional filter circuit 25. Therefore, by passing the output signal of the detection circuit 23 through the capacitor 24, the DC component is cut as shown in the waveform of FIG.
By inputting the output signal e in FIG. 13 to the additional filter circuit 25, noise components can be easily separated and used for detecting partial discharge. Then, the signal processed by the additional filter circuit 25 is transmitted to the display device 26, and the waveform is displayed on the display or displayed on the meter so that the presence or absence of the partial discharge can be detected.

When the ultrasonic sensor is configured as a sound collector having directivity, for example, the detecting device shown in each of the above embodiments is installed on an overhead wire, an insulator of a telephone pole, or a telephone pole. The present invention can be used for detecting partial discharge of a transformer, a branch, or the like. Then, even in a place where a lot of noise is generated, it is possible to separate and detect only the information related to the partial discharge by cutting the noise component. In addition, inside a closed box such as the inside of a cubicle, in order to detect partial discharge in equipment or cables, if an ultrasonic sensor having no directivity is installed inside the cubicle,
Partial discharge can be easily detected.

As a display device arranged in the detection device, a large number of lamps are arranged as in a conventional discharge detection device, and the intensity of the output information of the additional filter circuit is turned on. It can be indicated by the number of lamps. In addition, it is possible to use any display means such as a method in which the hand of the meter swings or a method in which a waveform is displayed on a television screen. In the case of a detection device fixedly arranged inside a cubicle or the like, a display device can be arranged in a centralized control room for a power supply so that partial discharge information of a large number of cubicles can be centrally managed. Further, in the display device, a reference for the magnitude of the waveform and the strength of the signal from the additional filter circuit is set in advance, and a means for sounding a buzzer when the reference value is exceeded is additionally provided. Calling attention to a technician is one way.

Further, by stopping the function of the present invention, it is possible to detect a mechanical vibration and a gas leak as in the conventional detector. By providing a changeover switch or the like in the detection device, it is possible to configure a detection device having two types of functions, such as a partial discharge detector or a gas leak detector.

[0029]

Since the detection device of the present invention is constructed as described above, a simple signal processing is used to convert the ultrasonic signal collected by the ultrasonic sensor into a discharge signal such as mechanical vibration or air vibration. Since the noises other than the above can be eliminated, the discharge can be accurately detected, and the inspection accuracy of the discharge can be improved. In addition, since the circuit used for the detection device can be configured as a simple circuit and the signal processing is easy, it can be easily incorporated into conventional equipment, and can be used in the same manner as the conventional device, increasing the discharge detection sensitivity. Thus, even minute discharge can be detected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a detection device.

FIG. 2 is an explanatory diagram of a signal of a partial discharge in the detection device of FIG. 1 and a processing waveform thereof.

FIG. 3 is an explanatory diagram of a noise signal and a processing waveform thereof.

FIG. 4 is an explanatory diagram of a signal waveform when noise is small.

FIG. 5 is an explanatory diagram of an output of a detection circuit that has processed the signal of FIG. 4;

FIG. 6 is an explanatory diagram of a signal waveform when noise is large.

FIG. 7 is an explanatory diagram of an output of a detection circuit that has processed the signal of FIG. 6;

FIG. 8 is a circuit diagram showing another configuration of the detection device.

FIG. 9 is an explanatory diagram of a signal processed by a reference voltage circuit.

FIG. 10 is an explanatory diagram of signal processing in a comparator.

FIG. 11 is a circuit diagram of another embodiment of the detection device.

12 is an explanatory diagram of an output signal of the detection circuit in FIG.

FIG. 13 is an explanatory diagram of an output signal of a capacitor.

FIG. 14 is an explanatory diagram of a partial discharge test circuit.

FIG. 15 is an explanatory diagram of a charging current waveform.

FIG. 16 is an explanatory diagram of a generation pattern of an ultrasonic wave.

FIG. 17 is an explanatory diagram of a waveform of a wind noise.

[Explanation of symbols]

Reference Signs List 1 detection device, 2 ultrasonic sensor, 2 bandpass filter, 4 detection circuit, 5 additional filter circuit, 6 display device, 8 applied power supply, 9
DUT, 10 detection device, 11 ultrasonic sensor, 12 bandpass filter, 13 detection circuit, 14 reference voltage circuit, 15 comparator, 16 additional filter circuit, 17 display device,
Reference Signs List 20 detection device, 21 ultrasonic sensor, 22
Bandpass filter, 23 detection circuit, 24
Capacitor, 25 Additional filter circuit, 26
Display device.

Claims (4)

[Claims] 1. A sensor for detecting an ultrasonic wave, an electromagnetic wave, or a charging current, a filter circuit for selectively passing and amplifying a signal from the sensor, and a rectifier for rectifying a signal transmitted from the filter circuit to form an envelope. A pattern recognition type partial discharge, comprising: a detection circuit that forms and outputs a signal; and a filter circuit that passes only a specific frequency selected from a signal output from the detection circuit, amplifies and outputs the signal. Detector. 2. From a signal output from the detection circuit,
2. The pattern recognition type according to claim 1, wherein a filter circuit that passes only a selected specific frequency, amplifies and outputs the same, and that passes and outputs a frequency twice as high as a commercial frequency is provided. Partial discharge detector. 3. A sensor for detecting an ultrasonic wave, an electromagnetic wave, or a charging current, a filter circuit for selectively passing and amplifying a signal from the sensor, and a rectifier for rectifying a signal transmitted from the filter circuit to form an envelope. A detection circuit that forms and outputs a signal; a comparison circuit that adjusts and outputs an output value of the detection circuit with a reference voltage value output from a reference voltage circuit; and a specific circuit selected from output information from the comparison circuit. A pattern recognition type partial discharge detector, comprising: a filter circuit that passes only a frequency, amplifies and outputs the amplified signal. 4. A sensor for detecting an ultrasonic wave, an electromagnetic wave or a charging current, a filter circuit for selectively passing and amplifying a signal from the sensor, and a signal for rectifying a signal transmitted from the filter circuit to form an envelope. A detection circuit that forms and outputs a signal, and a capacitor that cuts off the DC component of the output value of the detection circuit, amplifies and outputs the information, and outputs only a specific frequency selected from the output information from the capacitor to amplify the signal. A pattern recognition type partial discharge detector, comprising: