JPH07335445A - Insulation monitor of transformer - Google Patents

Abstract

PURPOSE:To provide an insulation monitor of transformer capable of detecting either the rapid vibration signals of partial discharge pulse generated in unstable timing with high precision or the generating phase, kind and judgement index, etc., of the partial discharge to be displayed. CONSTITUTION:Within an insulation monitor provided with a sensor 2, a filter circuit 3, a polarity control circuit 4, a P/H circuits 5A, 6A wherein the partial discharge pulse signals are successively converted by plural ends of A/D converters 6A, 6B while memorizing signal data relating to the high potential phase of the transformer 1 so as to detect the insulation state by computing the sum of the signal data within the voltage phase range of -30 deg.-90 deg. and 150 deg.-270 deg. to be displayed by a displayer 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulation state monitoring device for grasping the insulation state of a transformer.

[0002]

2. Description of the Related Art Various insulating materials are used and devised in a high-voltage insulating device of a transformer in order to enhance its insulating property (see, for example, Japanese Utility Model Laid-Open No. 56-134708). The life of the transformer is also determined by the insulation deterioration of the insulating material used. Therefore, in order to prevent sudden failure of the transformer and to use it with peace of mind, it is necessary to detect the initial stage of insulation deterioration such as partial discharge occurring in the insulation state. For this reason, in addition to the periodic inspections performed by stopping the transformer, an insulation state monitoring device that grasps the insulation state of the transformer during operation is used.

In a large oil-filled transformer, an electrical method using a plurality of ultrasonic sensors to grasp the insulation state, a current converter (hereinafter referred to as CT) using a ferrite core provided on the ground wire, and the like. In addition to the above, chemical methods such as analysis and quantification of gas components in oil are also used.

With the recent development of electronic equipment, Japanese Patent Laid-Open No. 4-151575 proposes an ultrahigh-speed analog-digital conversion device for detecting a partial discharge of a ground line. This is because the signal of the high frequency characteristic of partial discharge is subjected to ultra-high speed analog-to-digital conversion (hereinafter referred to as A / D conversion), data is taken in, data processing such as fast Fourier transform, digital waveform analysis, etc. The insulation state is determined by obtaining the energy amount and the number of occurrences of the partial discharge.

[0005]

However, the above-mentioned insulation condition monitoring device is not only complicated and expensive, but the chemical method is difficult to apply to a mold transformer or the like which is not an oil type insulation transformer. Further, the ultrasonic sensor of an electrical method is also difficult to use due to the mounting method, the sensor sensitivity when air is used as a conductive medium, and noise and noise of surrounding equipment. CT on the ground wire
The method of providing is to take out a signal of a narrow and low frequency band (several 100 KHz) in an analog manner as a noise countermeasure,
The charge amount of partial discharge was determined by comparing the maximum value of the pulse signal with the calibration pulse. For this reason, it is not possible to detect high frequency partial discharge pulses above 1 MHz, and
When the level of the pulse signal was small, but the number was large, it was not possible to accurately detect the judgment of the insulation state by partial discharge.

Further, the recently proposed ultra-high speed A / D converter requires not only expensive electric parts but also measures such as not being able to perform one partial discharge a plurality of times because it is too fast. , Requires complex processing. Further, since the relationship between the partial discharge and the high voltage phase is not clear, it is difficult to detect the generation phase and type of the partial discharge.

The present invention can be applied not only to oil-filled transformers but also to dry insulation transformers such as mold transformers, etc., without missing a high-speed vibration signal of a partial discharge pulse generated at indefinite timing, and unnecessary. Efficient detection without counting too many, noise is reduced and detected, and the type of partial discharge in which the partial discharge is occurring and the partial discharge judgment index, etc. can be detected and displayed. An object of the present invention is to provide a transformer insulation state monitoring device which is inexpensive and simple to calibrate using general electric parts such as a transformer.

[0008]

In order to achieve the above object, the insulation state monitoring apparatus of the present invention limits the effective high frequency component of the output signal of the partial discharge pulse from the sensor provided on the ground wire of the transformer. Means for sequentially adjusting the levels and adjusting the levels with a plurality of A / D converters, and detecting the voltage phase with reference to the 0 cross point when converting the high voltage signal of the transformer from negative to positive. A / D converted signal data is stored in association with the high voltage phase, and positive signal data in the voltage phase range of -30 ° to 90 ° and negative signal data in the voltage phase range of 150 ° to 270 ° are stored. From the above, the sum of the signal data whose polarity is positively inverted is obtained as a partial discharge index, and at least the larger one is used to determine the insulation state, and a display for partial discharge is provided.

Further, a pair of means for sequentially converting and a means for storing by a plurality of A / D converters are provided respectively, and the level-adjusted partial discharge signals whose polarity is inverted from positive to negative and to positive are A at the same timing. The configuration is such that the D / D conversion is performed and stored.

Further, the means for sequentially converting by the plurality of A / D converters has a peak hold time of 0.3 μs to 3 μs and a data acquisition interval of 4 μs or less. In addition, the positive and negative signal data obtained in succession leaves the previously obtained signal, and the signal data obtained at the same time leaves only the one with a large absolute value, and the others are changed to values that do not detect partial discharge. And

Further, a resistor or a resistor and an inductor connected in parallel is provided as a sensor on the ground line. In addition, the average value of a predetermined number or less is calculated from the larger absolute value of the positive and negative signal data within the range for each constant phase with reference to the 0 cross point when the high voltage voltage signal of the transformer changes from negative to positive. The type of partial discharge is determined from the pattern of the obtained signal data string.

In the multi-phase transformer, the positive signal data in the voltage phase range of -30 ° to 90 ° and the negative signal data in the voltage phase range of 150 ° to 270 ° of the transformer are used. A configuration in which if one of the partial discharge indices obtained from the signal data whose polarity is positively inverted is larger than the partial discharge index obtained in the same phase of another high voltage, the high voltage phase is determined as the partial discharge generation phase. And

At least one of the partial discharge generation phase, the type of partial discharge, and the index of partial discharge is displayed on the partial discharge indicator.

[0014]

According to the above configuration, the MH generated in the transformer
A partial discharge signal having many high frequency components equal to or higher than z can be directly detected from the ground line, and deterioration or deterioration of the signal is small and sensitivity is good. By sequentially capturing signals with a plurality of P / H circuits and A / D converters, it is possible to capture high-speed vibration signals of partial discharge pulses that occur at indefinite timing, and to capture without unnecessarily large numbers. High detection accuracy. Further, it is possible to distinguish signals due to vibrations that are difficult to separate, by knowing the delicate detection order by simultaneously detecting positive and negative data.
Further, since the peak hold time and the data acquisition time corresponding to the signal partial discharge pulse signal can be set, inexpensive general electric parts such as an A / D converter can be used. In particular, by processing by correlating the specific phase of the high voltage signal of the transformer with the partial discharge signal data, it is effective not only in removing noise components and unnecessary detection pulses, but also in the index and type of partial discharge. It is possible to provide a highly functional insulation state monitoring device for a transformer by detecting the generated phases and displaying them.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a block diagram of a partial discharge detection circuit of an insulation state monitoring apparatus according to a first embodiment of the present invention, in which 1 is a mold transformer and 2 is a ground wire as constituent elements. A resistor, a resistor in parallel with a resistor and an inductor, a sensor such as a high frequency CT or an electromagnetic wave sensor, 3 is a filter circuit including a filter and an amplifier, 4 is a polarity control circuit, 5A, 5
B is a P / H circuit, 6A and 6B are A / D converters, and 7 is a voltage 0 cross point detection circuit that detects a voltage 0 cross point when the high voltage of the V phase from the transformer 1 changes from negative to positive. , 8 is a timing control circuit, 9 is a data processing circuit including a microcomputer, a memory and the like, and 10 is a display for displaying the presence or absence of partial discharge and an alarm.

In the transformer insulation state monitoring apparatus including the above-described components, the frequency of the partial discharge signal from the sensor 2 is set to 0.1 MHz to 200 MH by the filter circuit 3.
z limit is performed to reduce noise and level adjustment is performed. Under the control of the microcomputer (not shown) of the data processing circuit 9, the polarity control circuit 4 initially passes only the positive signal to perform the data fetching process, and then reverses the polarity of the negative signal to pass the data to fetch the data. To do.

As shown in the timing chart of P / H and A / D conversion in FIG. 2, data acquisition is performed as described later. When a data acquisition signal is issued from 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 receives A / D converters 6A and 6B.
Of the P / H circuit A5A and the P / H circuits B5B and A in synchronization with the fall of the P / H control clock whose cycle is 2 μs.
The operation signals are sequentially supplied to the A / D converter A6A and the A / D converter B6B and are sequentially taken into the memory of the data processing circuit 9. It should be noted that the A / D converter has a conversion time of about 1 μs, and an inexpensive general 8-bit converter can be used. When the positive signal ends, the polarity control circuit 4 issues a polarity inversion command from the microcomputer, and in the same manner, negative signal data is obtained. In this way, the relationship with the phase of higher voltage than the address of the memory can be known.

The partial discharge pulse is 1 in the example shown in FIG.
Each signal 38 has a high-speed vibration waveform with a pulse width of about 10 ns, and the pulse interval is forcibly applied with a high voltage to generate a large number of partial discharges. Between the signals 37A and 37B shown in the pulse interval, 5.4 μs, and those with 10 μs or less are few, 100 μs
There are many things above. An example of experimentally generating a type that may cause partial discharge even in an actual transformer is shown. In a void type partial discharge, a single-phase test is performed using the test circuit shown in FIG. 5 (a). The high voltage of the transformer 17 is input as a voltage signal to the oscilloscope 24 having a frequency characteristic of 500 MHz or more via the voltage divider 23, while the high voltage is provided with the void 21 between the electrodes 20 and the periphery is made of the resin 19 such as epoxy. The resistance R = 100Ω and the inductance L = 2, which are applied to the covered void type sample 18 and are provided on the ground line.
A signal from the sensor 22 in which 5 μH is arranged in parallel is input to the oscilloscope 24, and the voltage data 25 shown in FIG.
And signal data 26 are obtained. This is considered to occur when there is a defect in the resin of the mold coil.
Similarly, in the creeping type partial discharge, a creeping type sample 27 prepared by providing an electrode 29 made of copper or the like on the surface of a solid 28 made of resin such as epoxy shown in FIG. 6 (b) voltage data 30 and signal data 31 are obtained. This may occur when the surface of the mold coil is deteriorated or contaminated. In the induced voltage type partial discharge, a high voltage is applied to the mold coil 34 in the test circuit shown in FIG. 7A, and the electrode 32 is provided at the tip of the ground wire provided with the sensor 22 so as to approach the mold coil 34. 7 occurs when
The voltage data 35 and the signal data 36 of (b) are obtained.
It is considered that this occurs when a conductive foreign substance approaches the mold coil or when a metal fitting for fixing the mold coil is loosened to form a gap with the mold coil.

The partial discharge signal data 26 shown in FIGS.
As can be seen from 31, 36, the partial discharge signals are mostly positive signal data in the high voltage phase range of -30 ° to 90 ° of the transformer and negative signal data in the high voltage phase range of 150 ° to 270 °. . The data of voltage phase −30 ° to 0 ° is 330 ° to 360 °. Therefore, the data processing in the data processing circuit 9 is performed by the positive signal data in the voltage phase range −30 ° to 90 ° and the high voltage phase range 150 ° to 90 °.
The sum of signal data obtained by inverting the polarity of the negative signal data at 270 ° is obtained as a partial discharge index, and the insulation state is determined by using at least the larger one. Since the magnitude of partial discharge is related to energy, the level and number of pulses of partial discharge, that is, the sum of signal data is detected. Further, since partial discharge has polarity, it may be judged by the partial discharge index of both of the phase ranges of the two voltages or by the maximum partial discharge index. However, the judgment criteria of the insulation state correspond to each. If the partial discharge index is smaller than the reference value 1 obtained by the experiment, it is normal, if it is larger than the reference value 1 and smaller than the reference value 2, it is judged as a light abnormality, and if it is larger than the reference value 2, it is judged as a heavy abnormality, and a signal is sent to the display unit 10. The LED provided in the part of the alarm display 40 of the panel 39 for displaying the partial discharge of the failure diagnosis display of FIG. 11 is turned on according to the determination result.

When the transformer 1 is a three-phase transformer, as shown in the partial discharge generation phase chart of FIG. 4, U-phase, V-phase,
Voltage phase of each phase of W phase -30 ° to 90 ° and 150 ° to 2
Based on the voltage phase when 70 ° changes from negative to positive V phase, the data of U phase is positive data of 210 ° to 330 °, negative data of 30 ° to 150 °, and data of W phase. Is positive data of 90 ° to 210 ° and negative data of 270 ° to 390 °. By subjecting these data to the same processing as described above, the insulation state of each phase can be known. To obtain the high-voltage phase, it is sufficient to use PT or low-voltage, etc. without using a voltage signal directly from the high-voltage terminal of the transformer, and to check and correct the phase difference between them and the high-voltage. .

If the P / H circuit is used, the peak hold time of the signal is set to 0.3 μs to 3 μs, and the data acquisition time including the A / D conversion time is set to 4 μs or less, the high-speed vibration signal of the partial discharge is increased. Not only can counting be prevented, but the memory capacity for recording data can be reduced, and the data processing time can be shortened.

In a multi-phase transformer, a sensor such as CT which can obtain a large vibration waveform cannot distinguish positive and negative signals from signals of other phases. Therefore, a resistor of several Ω or a resistor and an inductor in parallel are used. , It is desirable to use a sensor with less vibration in the opposite polarity.

As shown in the example of V-phase detection data in Table 1, the partial discharge signal is divided into positive and negative signal data in the range at every constant phase such as every 30 ° with the 0 cross point of the voltage as the division order. The type of partial discharge can be determined from the signal pattern obtained by obtaining an average value of a predetermined number or less such as 5 points from the largest.

[0024]

[Table 1]

In the example of Table 1, the positive signal patterns 92, 8
4, 51, 40 and negative signal patterns -88, -78,-
Since there is data in the voltage phase range of −30 ° to 0 ° at 53,0 and the size of the data gradually decreases, it can be determined that it is a void type partial discharge. In the case of the creeping type, the data is in the voltage phase range 0 ° to 90 °,
It has a mountain-like distribution and has positive and negative polarities. In case of induced voltage type, voltage phase range -30 ° ～
There is data at 90 °, the sizes are relatively uniform, and there are positive and negative polarities.

The display of the partial discharge of the failure diagnosis display is shown in FIG.
, And the generated phase display 41 and type display 4
2. It is convenient to use the index display 43 and the alarm display showing the degree of danger. Creepage type and induced voltage type partial discharge is likely to be improved during maintenance inspection. The types are indicated by numbers. It goes without saying that the determination result can be output to a connected device other than the display device.

(Embodiment 2) FIG. 3 is a block diagram of a partial discharge detection circuit of an insulation state monitoring apparatus according to a second embodiment of the present invention. A positive signal passed through the filter circuit 3 is a negative polarity cut circuit. A11A is passed and a plurality of P / H circuits A1
2A and P / H circuit B12B and A / D converter A13A
And the A / D converter B13B are sequentially processed, and the memory A14A
It is taken in as data without going through the microcomputer. On the other hand, the negative signal passed through the filter circuit 3 is inverted in polarity by the polarity inversion circuit 44 to the positive polarity, and then passed through the negative polarity cut circuit B11B in the same manner as in the case of the positive signal. P / H circuit C12C and P / H circuit D12D
Further, the data is sequentially processed by the A / D converter C13C and the A / D converter D13D, and is stored as data in the memory B14B without going through the microcomputer. In the data processing circuit 15, the memory A1
4A and the memory B14B are used, and the timing control circuit 16 processes positive and negative signals at the same time. By simultaneously processing the positive and negative signals in this way, the positive and negative data can be processed with the same partial discharge signal, which improves the detection accuracy.

When positive and negative signals are generated in the high-speed vibration waveform, one pulse is not only counted as many as two pulses, but in the case of a multi-phase transformer, it is mistaken for partial discharge of other phases.
As shown in the correction of the signal data of. In other words, the positive and negative signal data obtained in succession leaves the signal obtained earlier, the signal data obtained at the same time leaves only those with a large absolute value, and the others have values (normally 0) that do not detect partial discharge. change. If such processing is possible, partial discharge can be accurately detected even with a sensor having a large vibration waveform signal such as CT as a sensor provided on the grounding wire of the polyphase transformer. In addition,
Of course, the determination result is output to the display device or the connected device. Further, if the A / D converter can process positive and negative signals at the same time, the polarity control circuit and the negative polarity cut circuit are unnecessary and the circuit becomes simple.

[0029]

【The invention's effect】

1. As is clear from the above description, the insulation state monitoring device of the present invention can be applied to dry insulation transformers such as mold transformers as well as oil-filled transformers, and can detect partial discharge pulses generated at indefinite timings. Noise is reduced and detected efficiently and accurately without missing high-speed vibration signals and counting unnecessarily large numbers.

2. It is possible to detect and display the phase of partial discharge, the type of partial discharge, the judgment index of partial discharge, etc., which is convenient for maintenance and inspection. 3. The general-purpose electric parts such as an A / D converter can be used, and the structure is inexpensive and simple.

[Brief description of drawings]

FIG. 1 is a block diagram of a partial discharge detection circuit in an insulation state monitoring device according to a first embodiment of the present invention.

FIG. 2 is a timing chart of P / H and A / D conversion in the same insulation state monitoring device.

FIG. 3 is a block diagram of a partial discharge detection circuit in an insulation state monitoring device according to a second embodiment of the present invention.

FIG. 4 is a partial discharge generation phase chart.

5A is a test circuit diagram of a void type partial discharge, and FIG. 5B is a diagram showing data of a void type partial discharge.

6A is a diagram showing a creeping type sample of a creeping type partial discharge, and FIG. 6B is a diagram showing data of a creeping type partial discharge.

FIG. 7A is a test circuit diagram of an induced voltage type partial discharge. FIG. 7B is a diagram showing data of an induced voltage type partial discharge.

FIG. 8 is a graph showing a partial discharge pulse interval.

FIG. 9 is a graph showing a partial discharge pulse.

FIG. 10 is an explanatory diagram of correction of signal data.

FIG. 11 is a front view of a display section of partial discharge of the failure diagnosis indicator.

[Explanation of symbols]

 1 Mold Transformer 2 Sensor 4 Polarity Control Circuit 5A, 5B P / H Circuit 6A, 6B A / D Converter 7 Voltage 0 Cross Point Detection Circuit 8 Timing Control Circuit 9 Data Processing Circuit 10 Indicator

Claims (8)

[Claims] 1. A means for limiting a frequency component of an output signal of a partial discharge pulse from a sensor provided on a ground wire of a transformer, adjusting a level thereof, and sequentially converting the plurality of analog-digital converters. Means for detecting the voltage phase with reference to the 0 cross point when the high voltage signal of the transformer changes from negative to positive, and the analog / digital converted signal data is stored in association with the high voltage phase. Means for storing said positive signal data in said high voltage phase range −30 ° to 90 ° and said high voltage phase range 1
A means for determining the sum of the signal data in which the polarity is inverted from the negative signal data of 50 ° to 270 ° as the partial discharge index, and using at least the larger one to determine the insulation state and a partial discharge indicator. A transformer insulation condition monitoring device. 2. A pair of means for sequentially converting and means for storing by a plurality of analog-digital converters are provided respectively, and the level-adjusted partial discharge signals whose polarity is inverted from positive to negative and to positive are analyzed at the same timing. The insulation condition monitoring device for a transformer according to claim 1, wherein the device is subjected to goo-digital conversion and stored. 3. The means for sequentially converting with a plurality of analog-to-digital converters has a peak hold time of 0.3 μs to 3 μs and a data acquisition interval of 4 μs or less. An insulation condition monitoring device for the transformer described. 4. The positive and negative signal data obtained in succession leaves the signal obtained earlier, the signal data obtained at the same time leaves only the one with a large absolute value, and the others do not detect the partial discharge. The insulation state monitoring device for the transformer according to claim 2, wherein the insulation state monitoring device is changed. 5. The insulation condition monitoring device for a transformer according to claim 1, wherein a resistor or a resistor and an inductor in parallel are provided as a sensor on the ground wire. 6. An average of a predetermined number or less from a larger absolute value of positive and negative signal data in a certain phase at each constant phase with reference to the 0 cross point when the high voltage voltage signal of the transformer changes from negative to positive. 2. The insulation condition monitoring device for a transformer according to claim 1, wherein the type of partial discharge is determined from a pattern of a signal data string obtained by obtaining the value. 7. In a multi-phase transformer, obtained from positive signal data in the high voltage phase range of -30 ° to 90 ° and negative signal data in the high voltage phase range of 150 ° to 270 ° of the transformer. 2. The transformer according to claim 1, wherein if one of the partial discharge indexes is larger than the partial discharge index obtained in the same phase of another high voltage, the high voltage phase is determined to be a partial discharge generation phase. Device insulation condition monitoring device. 8. The insulation state monitoring device for a transformer according to claim 1, wherein at least one of the partial discharge generation phase, the type of partial discharge, and the index of partial discharge is displayed on the partial discharge indicator.