JPH08264331A - Partial discharge pulse data detection method - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a partial discharge pulse detection method that can reasonably separate the partial discharge pulse and the basic noise, and that can be detected when the partial discharge pulse is small at the initial stage of insulation deterioration [Configuration] Applied high voltage The phase is divided into multiples per 90 ° of the phase of the frequency and the sum of the absolute values of the data of each phase range is obtained. Obtain and determine the threshold value based on the maximum value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting partial discharge pulse data by separating basic noise from an output signal of a sensor for detecting partial discharge which is provided for insulation diagnosis of electric equipment.

[0002]

2. Description of the Related Art In high voltage electric equipment such as transformers, the life of the equipment is determined by the deterioration of the insulation material used. Therefore, in order to prevent a sudden failure of an electric device and to use it with peace of mind, it is necessary to detect an initial stage of insulation deterioration such as partial discharge generated in the insulating material.

With the recent development of electronic equipment, an ultrahigh-speed analog / digital converter for detecting a partial discharge of a ground line has been proposed (Japanese Patent Laid-Open No. 4-151575).
This is a high-speed analog / high-speed signal for partial discharge
Insulation status is obtained by obtaining data by digital conversion (hereinafter abbreviated as A / D conversion), data processing such as digital waveform analysis such as fast Fourier transform, and obtaining the amount of partial discharge energy per unit time and the number of occurrences. Is to be determined.

As a generally considered method, data obtained by A / D converting an output signal from a partial discharge detection sensor such as a high frequency CT provided on a ground line is arranged in time series as shown in FIG. 6 and applied to an electric device. For the data in the range (phase −30 ° to 360 °) corresponding to one cycle of the high voltage 25, the partial discharge pulse and the basic noise of the signal based on the signal 0 level that is the reference of the A / D converter are separated. By doing so, the amount of partial discharge energy can be obtained from the maximum partial discharge charge amount, the number of partial discharge pulses, and the sum of these products. Here, the basic noise means noise that exists over the entire phase, such as jitter.

[0005]

However, not only is the device for performing data processing such as digital waveform analysis such as the fast Fourier transform described above complicated and expensive, but if the frequencies of the partial discharge pulse and the basic noise are similar. Difficult to separate.

If a fixed threshold value is used to separate the partial discharge pulse and the basic noise shown in FIG.
Like the threshold A value, there is a partial discharge pulse that cannot be detected, or like the threshold C value, a partial discharge pulse and a lot of basic noise are detected. Therefore, it is difficult to find an appropriate threshold B value for separating the pulse and the basic noise. In particular, from the viewpoint of early detection of insulation deterioration, it is necessary to find it when the partial discharge pulse is as small as possible, but it is difficult to use a method that uses a fixed threshold value because the difference from the basic noise is small.

The present invention eliminates the above-mentioned conventional drawbacks and can be applied to electric equipment such as a transformer, and can efficiently separate partial discharge pulses and noise by a simple method, and can maximize the maximum partial discharge charge amount and partial discharge. An object of the present invention is to provide a partial discharge pulse data detection method capable of accurately obtaining the amount of partial discharge energy based on the number of pulses and the sum of their products, and detecting when the partial discharge pulse is small at the initial stage of insulation deterioration. And

[0008]

In order to achieve the above object, the method for detecting partial discharge pulse data according to the present invention uses an output signal from a sensor for detecting partial discharge, which is provided for insulation diagnosis of electric equipment. Absolute value of data in each phase range by sequentially converting with an A / D converter at fixed time intervals and storing as data, dividing into a plurality of phases per 90 ° of the frequency phase of the high voltage applied to the electric equipment. Calculate the sum, find the maximum absolute value among the data of the phase range where the sum of the absolute values is the minimum, and determine the threshold value that distinguishes the partial discharge pulse from the basic noise based on the maximum value. It is characterized by.

Further, in the partial discharge pulse data detection method of the present invention, the average value per pulse of the divided phase range data is calculated separately for positive and negative, and the phase for which the absolute value of the average value is the minimum is obtained. It is characterized in that positive and negative threshold values are set with reference to the one having the maximum absolute value in the range.

Further, the method for detecting partial discharge pulse data according to the present invention is a value including one of the threshold value obtained by the current measurement and at least one of the threshold values obtained by the previous and subsequent measurements. Among these, the maximum value is set as the threshold value.

Next, by using any one of the above-described detection methods, 0 when the phase of the high voltage power source of the single-phase electric equipment to which the detection method for partial discharge pulse data of the present invention is applied changes from negative to positive. It is characterized in that, in one frequency having a phase based on the cross point, the positive data in the range of 120 ° and the negative data in the range of 120 ° from the position shifted by 60 ° from the positive data range are used as the partial discharge data. It is a thing.

Further, using any of the above-mentioned detection methods,
In one frequency component of the phase based on the 0 cross point when the phase of the V phase of the high voltage power supply of the three-phase electric device to which the method for detecting partial discharge pulse data of the present invention is applied changes, A pair of positive data in the range of phase 120 ° and negative data in the range of 120 ° from a position shifted by 60 ° from the positive data range is defined as partial discharge pulse data of V phase, and 120 ° following the positive data of V phase. Of the positive data of the range and negative data of the V phase followed by the negative data of the range of 120 ° is defined as the partial discharge pulse data of the W phase.
12 following positive data in the range of 20 ° and negative data in W phase
The pair of negative data in the range of 0 ° is used as the U-phase partial discharge data.

[0013]

According to the above-mentioned means, the partial discharge generated in the electric equipment such as the mold transformer is generated at a specific phase of the applied high voltage which is the power supply frequency. , There is a phase range without partial discharge,
On the other hand, the basic noise has the same signal over the entire power supply frequency, so that the partial discharge pulse can be rationally detected by determining the threshold value with reference to the maximum signal in the range. Further, by separately detecting the positive and negative threshold values, it is possible to cope with the case where the center level of the output signal deviates from the signal 0 level of the processing circuit and the case where the basic noise level differs between positive and negative. Further, since the basic noise is liable to change, the optimum threshold value can be determined by using the maximum value of the threshold values of the measurement data at least before and after the partial discharge pulse is detected.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of detecting partial discharge pulse data according to the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a block diagram showing a data processing circuit for carrying out the method for detecting partial discharge pulse data according to the present invention, in which 1 is a mold transformer and 2 is a ground wire of the mold transformer 1. A sensor for detecting partial discharge, such as a high-frequency CT or an electromagnetic wave sensor, provided at 3, a signal processing device, 4
Is a filter circuit consisting of a filter and an amplifier, and the measurement range can be switched. 5 is a peak hold circuit (hereinafter P
/ H circuit), 6 is an A / D converter, 7 is a circuit for detecting a voltage 0 cross point when the applied high voltage, which is the power supply for the mold transformer 1, changes from negative to positive, and 8 is A timing control circuit, 9 is a data processing circuit including a microcomputer and memory, and 10 is a display for displaying the presence or absence of partial discharge and an alarm. Then, the frequency of the partial discharge signal from the sensor 2 is set to 0.1 MH by the filter circuit 4.
The level is adjusted while limiting noise to z to 200 MHz to reduce noise. Next, when the data acquisition signal is output due to the limitation of the microcomputer of the data processing circuit 9, the timing control circuit 8 receives the detection signal of the voltage 0 cross point detection circuit 7 and causes the A / D converter 6 to operate at 1 frequency. If there is, 16.7 ms (data acquisition time in the case of 60 Hz) is made operable, and the P / H circuit 5 and A / are synchronized with the fall of the P / H control clock whose cycle is 1 to 10 μs.
An operation signal is given to the D converter 6 and sequentially taken into the memory of the data processing circuit 9. The A / D converter 6 is capable of converting positive and negative signals at the same time, and an inexpensive general 8-bit converter having a conversion time of about 1 μs can be used. When the signal of the reset time of the P / H circuit 5 (time until the P / H level becomes 0) becomes a problem, two pairs of the P / H circuit 5 and the A / D
The converters 6 may be sequentially replaced and used. Next, the relationship between the data and the phase of the high voltage can be seen from the address of the memory that fetched the data. Further, the interval of the partial discharge pulse was 5.4 μs in the experimental example in which a large amount of partial discharge was forcibly applied by forcibly applying a high voltage. Therefore, the P / H circuit 5 can be designed according to the detection accuracy. Then, the signal processing circuit 9 performs data processing. As an example, in FIG. 2, the partial discharge pulse data P of the signal and the basic noise N are represented by the phase of the high voltage E of −30 ° to 33 °.
One frequency of 0 ° is phase-divided every 30 °, the sum of absolute values of data in each phase range is obtained, the phase range L having the smallest sum of absolute values is obtained, and the maximum value M in the phase range L is obtained. Is calculated, and the correction coefficient 1.1 is added to the maximum value M as a detection error amount.
The value multiplied by is processed as the threshold value S. The center level (ground level) of the output signal is normally adjusted so as to match the signal 0 level A of the signal processing circuit 9. Therefore, positive and negative data can be processed with the same absolute threshold value S having different polarities. Here, the phase reference is determined from the high voltage of the mold transformer 1, but the phase reference is not always necessary, that is, the phase may be made to correspond to time.

In the present embodiment, a plurality of phase ranges are obtained in the ascending order of the sum of absolute values of the divided phase range data, and the maximum value of the data of these phase ranges is used as the threshold value. This is because when the phase division range is large and the maximum basic noise cannot be found, or the detection error is reduced and the correction coefficient is set to 1.0.

(Embodiment 2) As shown in FIG. 3, by detecting the positive threshold value S1 and the negative threshold value S2 separately for detecting the partial discharge pulse P,
The central level S ′ of the output signal is the signal 0 of the data processing circuit 9.
It is possible to deal with the case where the basic noise level is different from the level So or the basic noise level is different between positive and negative.

Since the basic noise easily fluctuates, the optimum value of the threshold value that tends to fluctuate can be determined by using the maximum value of the threshold value of the measurement data at this time of detecting the partial discharge pulse and at least before or after the measurement data. I can decide.

(Embodiment 3) As shown in FIG. 4, in a single-phase mold transformer, the positive partial discharge is -30 ° to 90 ° with reference to the 0 cross point of the applied high voltage from negative to positive. Since the negative partial discharge is generated in the range of 150 ° to 270 °, the first embodiment described above is used.
If only the partial discharge within the above range is effective among the partial discharge pulses obtained by the processing of 1, the noise of the further partial discharge pulse can be removed. Further, as shown in FIG. 5, in the three-phase molded transformer, when the phase of the applied high voltage of the V phase is used as a reference, the positive partial discharge of the V phase is -30 as in the case of the single phase.
Negative partial discharge of 90 ° to 90 °, 150 ° to 270 °, positive partial discharge of W phase is 90 ° to 210 °, and negative partial discharge of 2
70 ° to 330 °, −30 ° to 30 °, 210 ° to 300 ° for positive partial discharge of U phase and 30 ° to 3 for negative partial discharge.
Since it occurs at 00 °, the partial discharge pulse in the phase range other than the partial discharge generation phase can be noise.

[0020]

【The invention's effect】

(1) As described above, the partial discharge pulse data detection method of the present invention has the following excellent effects.
A small level of partial discharge pulse close to the fundamental noise can be reasonably separated from the fundamental noise present over the entire power supply frequency by using an optimal threshold value. As a result, the amount of partial discharge energy can be accurately obtained from the maximum partial discharge charge amount, the number of partial discharge pulses, and the sum of these products.

(2) By detecting the positive and negative threshold values separately, when the center level of the output signal deviates from the signal 0 level of the processing circuit or when the basic noise level is different between positive and negative. Can handle.

(3) Since the relationship between the applied voltage and the partial discharge generation phase is known in the insulation diagnosis of electric equipment such as a mold transformer, noise can be further separated.

[Brief description of drawings]

FIG. 1 is a block diagram showing a data processing circuit implementing a partial discharge pulse data detection method of the present invention.

FIG. 2 is an explanatory diagram of data processing according to the first embodiment.

FIG. 3 is an explanatory diagram of data processing according to the second embodiment.

FIG. 4 is a timing chart showing a partial discharge generation phase of a single-phase molded transformer.

FIG. 5 is a timing chart showing a partial discharge generation phase of a three-phase molded transformer.

FIG. 6 is an explanatory diagram of conventional data processing.

[Explanation of symbols]

 1 Mold transformer (electrical device) 2 Sensor 3 Signal processing device 6 Analog / digital converter 9 Data processing circuit P Partial discharge pulse L Data sum Minimum phase range M Maximum value N Basic noise S Threshold value A, So Signal level S'Center level of signal S1 Positive threshold value S2 Negative threshold value

Claims (6)

[Claims] 1. An output signal from a sensor for detecting a partial discharge provided for insulation diagnosis of an electric device is sequentially converted at a constant time by an analog / digital converter and stored as data, and an applied voltage of the electric device is stored. 90 ° of frequency phase of voltage
The sum of absolute values of the data of each phase range is calculated by dividing it into a plurality of parts, and the maximum absolute value is found among the data of the phase range where the sum of absolute values is the minimum, and the maximum value is used as a reference. A method for detecting partial discharge pulse data, which comprises determining a threshold value for distinguishing a partial discharge pulse from basic noise. 2. The sum of absolute values of the divided phase range data is obtained by obtaining a plurality of phase ranges in ascending order, and the maximum absolute value of the data of these phase ranges is used as the threshold value. The method for detecting partial discharge pulse data according to claim 1. 3. An output signal from a sensor for detecting partial discharge provided for insulation diagnosis of electric equipment is sequentially converted by an analog / digital converter at regular time intervals and stored as data, and the applied voltage of the electric equipment is stored. 90 ° of frequency phase of voltage
Each phase range is divided into multiple parts to find the sum of the absolute values of the data in each phase range, and the divided phase range data is separately calculated for each positive and negative average value per pulse, and the absolute value of each average value is calculated. A method for detecting partial discharge pulse data, characterized in that positive and negative threshold values are set with reference to one having a maximum absolute value in a minimum phase range. 4. An output signal from a sensor for detecting partial discharge provided for insulation diagnosis of an electric device is sequentially converted at a constant time by an analog / digital converter and stored as data, and the applied voltage of the electric device is increased. 90 ° of frequency phase of voltage
Per phase division to find the sum of the absolute values of the data in each phase range, and either the threshold value obtained by the current measurement or at least the threshold value obtained by the previous or subsequent measurement A method for detecting partial discharge pulse data, wherein the maximum value among the values including is used as the threshold value. 5. A zero cross point when the phase of a high voltage power supply for a single-phase electric device changes from negative to positive by using the method for detecting partial discharge pulse data according to any one of claims 1 to 4. Partial discharge characterized by using positive data in the range of phase 120 ° and negative data in the range of 120 ° from a position shifted by 60 ° from the positive data range for one frequency of the reference phase as partial discharge data. How to detect pulse data. 6. The method for detecting partial discharge pulse data according to any one of claims 1 to 4, and 0 when the phase of the V phase of the high-voltage power supply of a three-phase electric device changes from negative to positive. At one frequency of the phase with the cross point as the reference, the phase 12
A pair of positive data in the range of 0 ° and negative data in the range of 120 ° from the position shifted by 60 ° from the range of the positive data is used as partial discharge pulse data of the V phase, and 1 is added following the positive data of the V phase.
12 following positive data in the range of 20 ° and negative data in V phase
A pair of negative data in the range of 0 ° is defined as partial discharge pulse data of the W phase, positive data in the range of 120 ° following the positive data of the W phase, and negative data in the range of 120 ° subsequent to the negative data of the W phase. A method for detecting partial discharge pulse data, wherein the pair of data is U-phase partial discharge data.