JPH0159549B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for locating the position of partial discharge (corona discharge) generated in electrical equipment such as a transformer, and a locating device for implementing this method.

In stationary induction equipment such as large-capacity oil-immersed transformers, reactors, or capacitors, the location of partial discharges can be located by detecting ultrasonic waves caused by partial discharges generated inside the equipment case from outside the case. It is. Conventionally, when locating the position of partial discharge in electrical equipment, the first
As shown in the figure, high voltage bushing 2 of electrical equipment 1
PD tap (voltage measurement terminal) provided on
Detector 4 connected to PF tap (test terminal) 3
The detected voltage and the ultrasonic signal obtained by amplifying the output of the ultrasonic detector 5 attached to the case 1a of the electrical equipment with the amplifier 6 are applied to the cathode ray tube oscilloscope 7, and the ultrasonic signal is obtained by the detector 4. The method used was to simply measure the time difference between the time when the corona pulse signal was detected and the time when the ultrasonic signal was detected by sweeping with the corona pulse signal included in the detected voltage. However, such a method has the disadvantage that it is difficult to distinguish between an ultrasonic signal generated by partial discharge and noise unrelated to partial discharge, resulting in poor S/N ratio and poor positioning accuracy. In order to improve the S/N ratio, it is possible to increase the sensitivity of the ultrasonic detector, but in that case, the detection sensitivity and the noise level also increase, so the improvement in the S/N ratio has been limited to a small amount. In addition, when trying to obtain a large corona pulse signal to improve the detection accuracy of partial discharges, the voltage applied to the device under test must be increased, which poses problems such as an extremely dangerous situation in terms of insulation strength. Therefore, it was not possible to expect much improvement in positioning accuracy. Furthermore, with the above method, it is difficult to accurately locate the position of partial discharge when a plurality of corona pulse signals are detected successively.

An object of the present invention is to provide a partial discharge position locating method for electrical equipment that can accurately locate a specific partial discharge that occurs frequently and requires locating even when a plurality of corona pulse signals occur in succession, and a method for locating the partial discharge position of electrical equipment. The object of the present invention is to provide a locating device for carrying out this invention.

The method of the present invention detects a pulse signal caused by a partial discharge generated in an electrical device, detects an ultrasonic wave caused by a corona generated within the device, and supplies the repeatedly generated pulse signal to a peak value and phase selector. By adjusting the phase and peak value range to be selected by the selector, a corona pulse signal is obtained in correspondence with a specific pulse signal having a predetermined phase and a peak value within a predetermined level range, and the corona pulse signal is obtained. Every time a corona pulse signal is detected, an ultrasonic signal generated within a predetermined time period after the corona pulse signal is detected is stored, and the stored ultrasonic signal is averaged to obtain a signal included in the ultrasonic signal. a part of the electrical equipment by substantially removing noise caused by the electric device, obtaining a corona sound detection signal, and determining a time difference between a time when the specific corona pulse signal is detected and a time when the corona sound detection signal is detected. This method is characterized by locating the position where the discharge occurs.

Further, the orientation position of the present invention includes a pulse detector that detects a pulse signal due to a partial discharge generated in an electric device, an ultrasonic detector that detects an ultrasonic wave due to a partial discharge generated in the electric device, and the pulse detector. a wave height value and phase selector for obtaining a corona pulse signal corresponding to a specific pulse signal having a predetermined phase and a wave height value in a predetermined level range among the repeatedly generated pulse signals detected by the corona pulse signal; a memory device that stores an ultrasonic signal detected by the ultrasonic detector within a certain time period after the corona pulse signal is generated each time the corona pulse signal is generated; and an averaging process for the ultrasonic signal stored in the memory device. an averaging processor that removes noise and outputs it as a corona sound detection signal; the wave height value and phase selector is configured to be able to adjust the phase and wave height value to be selected; The present invention is characterized in that the position where the partial discharge occurs is located from the time difference between the corona pulse signal and the corona sound detection signal.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram schematically showing an example of the configuration of a position locating device that implements the method of the present invention. It is. A well-known PD tap (or PF tap) 3 is installed at the base of the high voltage bushing 2 attached to the upper part of the case of the transformer 1.
is provided. PD tap or PF tap is a type of voltage transformer output terminal that has an electrode electrostatically coupled to the bushing conductor, from which the voltage applied to the bushing conductor can be divided and taken out. It's becoming like that. PD
The signal S ₁ obtained from the tap 3 is input to a power frequency signal detector 10 and a pulse detector 11 . The power supply frequency signal detector 10 is a circuit that removes pulse-like signals such as pulses caused by partial discharge from the input signal _S1 and outputs a power supply frequency signal _S2 . Become. The pulse detector 11 is a circuit that removes the power supply frequency signal from the input signal S ₁ and outputs a pulse signal S ₃ , and is constituted by, for example, a high-pass filter that passes only pulses.

The power supply frequency signal S ₂ and the pulse signal S ₃ are input to the peak value phase selector 12 . Peak value phase selector 1
2, as shown in FIG. 3, a gate signal generation circuit 12a that generates a rectangular wave gate signal _S4 having a desired phase and a desired time width with reference to the zero point of the input power supply frequency signal _S2 ; , a corona pulse detection circuit 12b that outputs only pulses whose peak values are within a predetermined range out of the pulse signal _S3 as a corona pulse signal _S5 , a gate signal _S4 , and a corona pulse signal _S5 .
and an AND gate 12c which receives as input. Here, the gate signal generation circuit 12a is composed of, for example, a phase selection circuit 12a ₁ that determines the phase at which the gate signal is generated, and a gate width selection circuit 12a 2 that determines the time width of the gate signal, and includes a phase selection circuit 12a ₂ that determines the time width of the gate signal, and a phase selection circuit 12a 2 that determines the phase at which the gate signal S ₄ is generated. The time width of the gate signal _S4 can be adjusted arbitrarily. The corona pulse detection circuit 12b includes, for example, a polarity selection circuit 12b ₁ that selects the polarity of the pulse to be detected and a pulse height discrimination circuit 12b ₂ that discriminates whether the peak value of the pulse is within a predetermined level range. The discrimination level in the circuit _12b2 can be set arbitrarily. The AND gate 12c emits an output when the gate signal S ₄ and the corona pulse signal S ₅ are input simultaneously, and outputs a trigger pulse signal from the peak value phase selector 12.
Output S ₆ .

An ultrasonic detector 5 that electrically detects ultrasonic waves generated within the case 1a is attached to the side surface of the case 1a, and an ultrasonic signal _S7 obtained from the ultrasonic detector 5 is amplified by an amplifier 6. . The ultrasonic signal S ₇ ' amplified by the amplifier 6 is input to the signal wave storage 13 together with the pulse signal S ₃ and the trigger pulse signal S ₆ . The signal wave storage device 13 always performs a sampling operation of the ultrasonic signal S ₇ ′, and every time the trigger pulse signal S ₆ is input, the signal wave memory 13 temporarily stops the sampling operation after a predetermined time period set from the time of input. It's starting to stop. Then, the sampled value is converted into a digital quantity and temporarily written into the semiconductor memory, and at the same time, the pulse signal _S3 synchronized with the trigger pulse signal _S6 is also converted into an ultrasonic signal.
The sampled value of S ₇ ′ is written to the semiconductor memory in a state differentiated from the digital quantity. In this case, digital conversion of ultrasonic signals is performed within a predetermined time period at extremely high speed (for example, 10 ns/word) and with high resolution (for example, 8 bits). The signal wave storage device 13 also reads out the digitally converted and stored ultrasonic signal with a delay of the time necessary for the averaging processor (to be described later) to perform the calculation, and again reads out the analog converted ultrasonic signal (analog Send out ultrasonic signal) S ₇ ″.

The analogized ultrasonic signal S ₇ ″ read out from the memory 13 is transferred to the averaging processor 14. The averaging processor 14 calculates the number of times the values of the analog signals transferred from the memory 13 are added. This is an arithmetic unit that performs calculation (averaging processing) to divide the signal by , and outputs the averaged signal as the corona sound detection signal _S8 . After starting the transfer of the standardized ultrasonic signal S ₇ ″, the stored pulse signal S ₃ is transferred after a certain period of time corresponding to the calculation time of the averaging processor 14.
(a pulse signal synchronized with the trigger signal S ₆ ), converts it into analog, and sends it out as a pulse signal S ₃ ′ (analog signal). The signal S ₃ ′ and the corona sound detection signal S ₈ are respectively connected to two vertical axis terminals V 1 and ₁ of a waveform observation device 15 consisting of a synchroscope or an oscilloscope capable of observing two phenomena simultaneously.
Input to _V2 . As a result, the waveform observation device 15
The pulse signal S ₃ ′ and the corona sound detection signal S ₈ are simultaneously displayed on the time axis of the same time scale on the cathode ray tube surface.

In FIG. 2, the X, Y, and Z terminals are terminals for recording the respective output signals of the power frequency signal detection 10, pulse detector 11, and amplifier 6 in a data record (not shown) in advance, for example, by averaging processing. It is used to collect various data before performing.

A to I in Figure 4 refer to Figures 2 and 3.
The signal waveforms at each part of the figure are shown with time T taken as the horizontal axis. The position locating method of the present invention will be explained below with reference to these signal waveform diagrams and FIGS. 2 and 3. Now, for the corona test of the electrical equipment 1, the applied voltage (sine wave) is increased. If a partial discharge occurs inside the case due to the applied high voltage, a pulse signal S3 is superimposed on the sinusoidal power frequency signal _S2 at the PD tap ₃ of the high voltage bushing 2, as shown in Figure 4A. A signal S ₁ is obtained. The pulse signal _S3 includes a plurality of pulses having various random peak values, and these pulses include pulses caused by partial discharge as well as pulses caused by other noises. Among the pulses included in the pulse signal _S3 , those due to partial discharge occur approximately periodically in a region where the instantaneous value of the power supply frequency signal _S2 is relatively high, and noise occurs non-periodically. Partial discharges that pose problems in terms of performance in electrical equipment (partial discharges that require positioning) occur almost periodically and frequently, and occur in regions where the instantaneous value is high for several cycles. There is no need to locate a partial discharge that disappears after that, or a partial discharge that happens to occur in a certain cycle. The problematic partial discharge occurs approximately every cycle and at a high frequency approximately periodically in a region where the instantaneous value of the power supply frequency signal _S2 is relatively high. Therefore, when locating the partial discharge position, first observe the waveform of the pulse signal _S3 with an oscilloscope, etc., identify the partial discharge that occurs approximately periodically with the highest frequency, and then identify the partial discharge. Locate the location of partial discharge.

When the above signal S ₁ is input to the power frequency signal detector 10 and the pulse detector 11, a sine wave power frequency signal S ₂ is obtained at the output side of the power frequency signal detector 10 as shown in FIG. 4B. Further, on the output side of the pulse detector 11, a pulse signal _S3 containing a large number of pulses is obtained as shown in FIG. 4C. The power supply frequency signal S ₂ and pulse signal S ₃ obtained in this way are input to the peak value phase selector 12, and the power supply frequency signal
S ₂ and pulse signal S ₃ are applied to the gate signal generation circuit 12a and corona pulse detection circuit 12b of the peak value phase selector 12, respectively. As shown in FIG. 4D, the gate signal generation circuit 12a generates a constant phase signal selected with reference to the zero point of the power supply frequency signal _S2 .
At t ₁ , t ₅ , t ₁ , t ₅ , . . . , a rectangular waveform gate signal S ₄ having a selected constant time width is generated. The phases t ₁ , t ₅ , ... for generating this gate signal are set to phases near where the instantaneous value of the power supply voltage is at a level that causes partial discharge, and the instantaneous value of the power supply voltage is set at a level that is at a level that causes partial discharge. The generation position of the gate signal is adjusted and set so that the gate signal _S4 is generated during a certain period.

If P ₁ is the pulse caused by the problematic partial discharge among the many pulses shown in _FIG . Pulses that occur approximately periodically in every cycle but do not cause any other problems, such as pulse P ₂ , may occur following pulse P ₁ for 3 cycles as shown in the figure, but then disappear or occur occasionally. The extent of this is to do so. Therefore, by observing the waveform of the pulse signal _S3 for a certain period of time, it can be seen from the frequency of pulse occurrence that the pulse _P1 is due to a problematic partial discharge. The following explanation will proceed assuming that the pulse generated by the partial discharge in question is _P1 .

The corona pulse detection circuit 12b first selects only one of the positive and negative polarity pulses of the pulse signal _S3 using the polarity selection circuit 12b1, and then selects only one of the positive and negative polarity pulses of the pulse signal _S3 , and then uses the pulse height discrimination circuit _12b2 to select whether the peak value is within a predetermined range. Extract only the pulse. In this embodiment _{, only} pulse signals of positive polarity are selected in _{FIG .} .
As a result, a corona pulse signal consisting of only two pulses P 1 ′ and P ₂ ′ corresponding to pulses P ₁ and P ₂ generated by partial discharge is output to the output side of the corona pulse detection circuit _12b as shown in FIG. 4E. Get _S5 . Here, the discrimination levels a ₁ and a ₂ are set for the purpose of extracting only relatively large pulse signals S ₃ of various sizes generated at different phases and meeting certain conditions.
A lower limit level is set, and is set so that it is possible to distinguish between pulse signals that appear continuously in the same phase and with relatively the same magnitude, and pulse signals that occur discontinuously and have different phases. .
When this corona pulse signal S ₅ is input to the AND gate 12c together with the gate signal S ₄ and both signals S ₄ and S ₅ exist simultaneously, the phase t ₂ of the corona pulse signal S ₅ is changed as shown in FIG. 4F. a specific pulse that occurred at
P ₁ ′, that is, the phase in each period of the power supply voltage waveform
A trigger pulse signal S ₆ is periodically generated in response to the first pulse P ₁ ′ (pulse due to problematic partial discharge) extracted from t ₁ to _{t 4} .

On the other hand, the waveform of the ultrasonic signal _S7 obtained at the output side of the ultrasonic detector 5 is as shown in FIG. 4G, for example.
The waveform contains noise outside of ultrasonic waves (corona sound) caused by partial discharge. Note that the time scale in Figure 4G and the time scale in Figure 4F are unrelated;
Figure G shows a much shorter time range than Figure 4F. This ultrasonic signal S ₇ is amplified by the amplifier 6 to form an ultrasonic signal S ₇ ', which is input to the signal wave storage 13 together with the trigger pulse signal S ₆ and pulse signal S ₃ described above. In this case, the signal wave storage device 13 stores the ultrasonic signal S ₇ ' triggered by the trigger pulse signal S ₆ for a predetermined time period from the input point of the trigger pulse signal S ₆ every time the trigger pulse signal S ₆ is input. It is periodically sampled and stored. Therefore, every time a specific pulse P ₁ is generated and a trigger pulse signal S ₆ is generated, the ultrasonic signal S ₇ ' detected within a certain period of time after the generation point is stored in the signal wave memory 13.
The ultrasonic signal S ₇ ' input to the signal wave storage device 13 is digitally converted and written into the memory.

The signal wave storage device 13 temporarily stops the sampling operation after a predetermined time period from the time when the trigger pulse signal S ₆ is input, reads out the digitally converted ultrasound signal stored during this predetermined time period, and then keeps the sampling operation constant after that. After a time delay, the digitally converted ultrasonic signal is converted into analog again and the analogized ultrasonic signal S ₇ '' is transferred to the averaging processor 14 .

The averaging processor 14 adds an average of n analog ultrasonic signals S ₇ '' for each input of the trigger pulse signal S ₆ , divides the resulting value by n, and averages the ultrasonic signals S ₇ ''. . When such averaging processing is performed, only the ultrasonic signal generated by the partial discharge corresponding to the specific pulse P ₁ that occurs periodically with high frequency remains, and irregularly occurring noise and specific pulses are left behind. The ultrasonic signals generated by partial discharges corresponding to pulses that occur less frequently than pulse P ₁ (pulse P ₂ in this example) are canceled and removed, and Only the detection signal of the ultrasonic wave generated by the partial discharge corresponding to pulse _P1 is distinguished and extracted. The analog signal after being averaged in this way is the corona sound detection signal.
It is given to the waveform observation device 15 as _S8 . This corona sound detection signal ₈ is displayed in a waveform as shown in FIG. 4I, for example.

On the other hand, after the storage device 13 starts transferring the analogized ultrasonic signal S ₇ ″ to the averaging processor 14, the stored pulse is delayed by a certain period of time corresponding to the calculation time in the averaging processor 14. The signal S ₃ (corona pulse signal synchronized with the trigger pulse signal S ₆ , in this example, the corona pulse signal P ₁ ) is read out and converted into an analog signal as shown in FIG. _4H . Therefore, first, the _fourth
The pulse signal S ₃ ' in FIG. H is input, and then, after a certain time delay Δt, the corona sound detection signal S ₈ is input to the other vertical axis V ₂ . The waveform observation device 15 displays the pulse signal S ₃ ' (FIG. 4H) and the corona sound detection signal S ₈ (FIG. 4I) on the same time scale on the cathode ray tube surface. The corona sound detection signal S ₈ is generated with a delay of a delay time Δt from the pulse signal S ₃ ′. This delay interval Δt
is the time required for the ultrasonic wave caused by the partial discharge to propagate to the position of the ultrasonic detector 5 after the partial discharge occurs, and this delay time Δt is calculated by the propagation velocity of the ultrasonic wave and the propagation coefficient due to the transmission medium. By multiplying by , the distance from the ultrasonic detector to the position where the partial discharge occurs can be determined, and the position where the partial discharge occurs can be located.

In the above explanation, the width and phase of the gate signal S ₄ are adjusted to include both pulses P ₁ and P ₂ , and the pulses P ₁ ', corresponding to these pulses P ₁ and P ₂ are
Assume that the position of the partial discharge corresponding to pulse P 1 is located by obtaining a corona pulse signal S ₅ consisting only of P ₂ ′ and generating a trigger pulse signal S ₆ corresponding to the first pulse P _{1 ′} . , gate signal S ₄
The time width and phase of can be adjusted arbitrarily, so if pulse P ₂ of pulses P ₁ and P ₂ is a pulse that occurs approximately periodically with high frequency, this pulse P ₂
It is also possible to locate the position of the partial discharge corresponding to the pulse _P2 by setting it as a specific pulse. That is, when locating the occurrence position of a partial discharge corresponding to pulse P ₂ , the time width of gate signal S ₄ is set to be narrow so that only pulse P ₂ is included, and the time width of gate signal S _{4 is narrowed so that only pulse P 2} is included. The phase of the gate signal _S4 is adjusted so that only the pulse _P2 is included inside the gate signal S4. At this time, the trigger pulse signal S ₆ and the pulse signal S ₃ are generated at the position where the pulse P ₂ is generated. In addition, the averaged corona sound detection signal S ₈ corresponds to the ultrasonic wave generated by the partial discharge corresponding to the pulse P ₂ that occurs almost periodically with high frequency ( (The ultrasonic signal corresponding to the pulse P ₁ is canceled by the averaging process.) Therefore, it is possible to locate the position where the partial discharge corresponding to the pulse P ₂ occurs.

In addition, multiple ultrasonic detectors are attached to different locations on case 1a, and the distance from each ultrasonic detector to the position of the partial discharge is measured using the same method as above, and the distance from each ultrasonic detector to the position of the partial discharge is measured with the position of each ultrasonic detector as the center. It goes without saying that the position of the partial discharge can be located with even higher accuracy by drawing circular arcs with a radius equal to the distance measured by the distance and finding the intersection of these circular arcs.

Although an oscilloscope was used as the waveform observation device 15 in the above embodiment, a waveform storage device such as an XY recorder may be used instead of this oscilloscope.

As described above, the partial discharge position locating method and the locating device of the present invention provide a peak value and phase selector and adjust the range of the phase and peak value that the selector should select. Any one pulse signal that is repeatedly generated from the pulse signals is specified, a corona pulse signal is generated in response to this specified pulse signal, and each time the corona pulse signal is repeatedly generated, the corona pulse signal is Ultrasonic signals generated within a predetermined time period are stored and averaged to obtain a corona sound detection signal, and the time when the corona pulse signal is generated is compared with the time when the corona sound detection signal is detected. By determining the time difference, it is possible to accurately detect the propagation time of the ultrasonic wave from the position where the partial discharge occurs to the position of the ultrasonic detector, and to accurately locate the position where the partial discharge occurs. In particular, it has the ability to arbitrarily identify a pulse signal caused by any one partial discharge.
Even if pulse signals due to partial discharges and pulse signals due to noise occur in various different phases, it is possible to identify pulse signals due to partial discharges that require localization.
This has the effect of accurately locating the location where the specific partial discharge occurs.

[Brief explanation of drawings]

FIG. 1 is a block diagram explaining a conventional method, FIG. 2 is a block diagram showing an example of the configuration of an apparatus for implementing the method of the present invention, and FIG. 3 is a block diagram showing an example of the configuration of a peak value phase selector used in the present invention. The block diagrams shown in FIGS. 4A to 4G and G' to I are diagrams showing examples of signal waveforms in each part of FIGS. 2 and 3. 1...Electrical equipment, 5...Ultrasonic detector, 6...
Amplifier, 10...Power frequency signal detector, 11...
... Pulse detector, 12 ... Peak value phase selector, 1
3...Signal wave storage device, 14...Averaging processor, 1
5... Waveform observation device, S ₂ ... Power frequency signal, S ₃ ...
...pulse signal, S ₄ ... gate signal, S ₅ ... corona pulse signal, S ₆ ... trigger pulse signal, S ₇ ... ultrasonic signal, S ₇ ″ ... analogized ultrasonic signal, S ₈ ...
...Corona sound detection signal.

Claims (1)

[Claims] 1. Detecting a pulse signal due to a partial discharge generated in an electrical device and detecting an ultrasonic wave due to a partial discharge generated within the device, and applying the repeatedly generated pulse signal to a peak value and phase selector. A corona pulse signal is obtained in correspondence with a specific pulse signal having a predetermined phase and a peak value within a predetermined level range by adjusting the phase and peak value range to be selected by the selector. Each time the corona pulse signal is detected using the pulse signal as a reference, an ultrasonic signal emitted within a predetermined time period after the corona pulse signal is detected is stored, and the stored ultrasonic signal is averaged. thereby substantially removing the noise contained in the ultrasonic signal to obtain a corona sound detection signal, and determining the time difference between the time when the specific corona pulse signal is detected and the time when the corona sound detection signal is detected. 1. A method for locating a partial discharge position in an electrical device, comprising locating a position where a partial discharge has occurred in the electrical device by determining . 2. A pulse detector that detects a pulse signal due to a partial discharge generated in an electrical device, an ultrasonic detector that detects an ultrasonic wave due to a partial discharge generated in the electrical device, and a repeatedly generated pulse signal detected by the pulse detector. a wave height value and phase selector for obtaining a corona pulse signal corresponding to a specific pulse signal having a predetermined phase and a wave height value within a predetermined level range among the pulse signals, and detecting the corona pulse signal with reference to the corona pulse signal; a memory device that stores an ultrasonic signal detected by the ultrasonic detector within a predetermined time period after the corona pulse signal is generated each time the corona pulse signal is generated; and an averaging process for the ultrasonic signal stored in the memory device. and an averaging processor that removes noise and outputs it as a corona sound detection signal, and the wave height value and phase selector is configured to be able to adjust the range of the phase and wave height value to be selected, A partial discharge position locating device for electrical equipment, characterized in that a position where a pulse is generated due to partial discharge is located based on a time difference between the specific corona pulse signal and the corona sound detection signal.