JPS61147170A - Measuring instrument for partial discharge - Google Patents

Abstract

PURPOSE:To remove the influence of external noises and to obtain hgih detec tion sensitivity to a void discharging pulse and a partial discharging pulse in SF6 gas by constituting an analog measuring device which includes plural phase shift subtracting means and a noise eliminating means. CONSTITUTION:A noise eliminating circuit 50 is provided at the output side of a band amplifier 30 with a 50-1,000MHz passing frequency band. The circuit 40 constitutes an analog measuring instrument by cascading the 1st and the 2nd phase shift subtracting means 11 and 14 consisting of delay circuits 12 and 15 with 10-30ns delay time and subtracting circuits 13 and 16 with subtract input and output signals of the circuits 12 and 15 are further connecting the noise eliminating means 17 consisting of a delay circuit 18 with delay time correspoding to the total delay time of both phase shift subtracting means and a multiplying circuit 19 which multiplies input and output signals of the circuit 18. Consequently, an external noise of <=50MHz is eliminated to improve its S/N, and partial discharging pulse with a pulse width ns is processed without variation of its original waveform, so the resolution of the pulse is increased, so that even a fine partial discharging pulse is detected.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a gas insulated hermetic switchgear, a gas insulated cable,
Gas insulated electrical appliances such as gas insulated transformers, 11 high voltage rotating machines,
The present invention relates to a partial discharge measuring device for measuring partial discharge pulses generated in high voltage equipment such as solid insulated equipment such as resin molded transformers, distinguishing them from electrical noise.

[Prior art and its problems]

Conventionally, this type of measuring instrument was an ERA type measuring instrument (ERA
-5 type, band frequency 10 to 300 KHz), tuning type % type band side wave number 355 to 445 KHz) are widely known,
1. From Jin and K who detect the above band frequency component among the frequency components of the partial discharge pulse. Partial discharge in oil, partial discharge in air, and void discharge with different upper frequency components.

It is configured to be able to measure partial discharge pulses such as SF and partial discharge in gas.

On the other hand, in a partial discharge test at the installation site of the electrical equipment under test, electrical noise, such as a power line corona pulse, is detected superimposed on the partial discharge pulse.

Manufactured by a company where an important issue is how to distinguish or eliminate noise pulses whose upper limit frequency component is close to that of partial discharge pulses, such as thyristor commutation pulses.
type and CD-5 type) are known.

FIG. 9 is an explanatory diagram of a partial discharge test circuit using a conventional partial number factor measuring device. In the figure, a detection impedance 4A is provided on the ground potential side of an electrical equipment under test 2 to which an AC high voltage is applied by a high voltage power supply 1 and a bypass capacitance 3 such as a coupling capacitor.

4B is connected, the partial discharge pulse generated in the device under test 2 flows through the two detection impeders 4A and 4B in opposite directions as shown by solid arrows.
For example, noise pulses that enter from the high voltage power supply side flow in the same direction as shown by the dashed arrows, so it is necessary to determine whether the pulses detected at the same time are of the same polarity or opposite polarity. It is possible to distinguish between pulses and noise pulses (called a balanced circuit).

Reference numerals 5 to 7 logic control discriminators amplify specific frequency components of the detected pulses (5A, 5B) and convert them into logic pulses (6A, 6B) of the same polarity.

It is configured to determine the reverse polarity and output a gate pulse (7), and the gate circuit 8 of the tuned partial discharge measuring instrument 8
The output display circuit 8BK is configured to output only the partial discharge pulse by controlling on/off of A by the gate pulse. By configuring it as described above, the output of intermittent noise can be prevented. partial discharge pulses can be detected. However, since the time width of the gate pulse is usually set to 10 to several tens of microseconds, the gate circuit may 8A remains mostly closed,
There is a problem that measurement of partial discharge pulses becomes impossible. To avoid this, if the input signal level is narrowed down to such a level that only large noise noises are input, the detection sensitivity of partial discharge pulses will decrease. Void discharge with a small partial discharge charge amount of several tens of PCs) (Russ,
sr.

[Objective of the Invention] The present invention has been made in view of the above-mentioned situation, and eliminates the influence of external noise and detects void discharge nozzle and 8F. ,
The object of the present invention is to provide a partial discharge measuring device that has high detection sensitivity for partial discharge nozzles in gas.

[Key points of the invention]

The present invention is characterized in that, while the upper limit of frequency components of SF, partial discharge pulses in gas, and void discharge pulses are distributed in a high frequency region exceeding 50 MHz, the frequency components of thyristor noise, partial discharge pulses in oil, etc. Focusing on the fact that the upper limit region of is distributed in the frequency region of approximately 10 MH2 or less, we created a void discharge pulse and an 8F partial discharge pulse in gas (hereinafter abbreviated as partial discharge pulse) using a band amplification circuit with a pass frequency band of 50 MHz to 100100 O. is amplified to a predetermined level, and is provided on the output side of the band amplification circuit, and the incoming curls are amplified to a predetermined level with a pulse width of, for example, 10~
For example, two sets of phase shift subtraction means connected after each other, consisting of a delay circuit that delays the delay by 30% and a subtraction circuit that uses the input/output signals of this delay circuit as input signals, calculate the duration compared to the delay time. A delay circuit that reduces the peak value and shortens the pulse width of a long noise pulse, is provided on the output side of the phase shift subtraction means, and has a delay time corresponding to the total delay time of the phase shift subtraction means, and an input/output of this delay circuit. A noise canceling means consisting of a multiplication circuit that takes the signal as an input signal detects the overlap between the input pulse and the delayed pulse, cancels the noise pulse in the input pulse, and increases the number of noise pulses by passing through the delay circuit. Only one partial discharge pulse (void discharge) (Russ, SF, partial discharge pulse in gas) in a partial discharge pulse train is output.

[Embodiments of the invention]

The present invention will be explained below based on one embodiment.

FIG. 1 is a block diagram showing an embodiment of the partial discharge measuring device of the present invention. This figure shows a state in which a measuring device is connected to a test circuit for measuring a portion consisting of a sample 2° and a detection impedance 4.

In the figure, there is an input circuit including a 10-digit impedance matching circuit, etc., and 60 is a band amplifier.
When measuring partial discharge in an insulating gas such as gas, the pass frequency band is set to 50 to 1000100O. 40 is a noise removal circuit provided on the output side of the band amplifier 60, and includes a first phase shift subtraction means 11, a second phase shift subtraction means 14, which are connected in cascade with each other. The noise canceling means 17 and the output circuit 20 also include a phase shift subtracting means 11 and a delay circuit 1 comprising a delay line or the like that delays the input signal by at least the pulse width of the partial discharge pulse.
2 and 15, and an analog subtraction circuit 1'5 and 16 that subtracts the output delayed signal from the input signal of the delay circuit. A delay circuit 18 having
and an analog multiplier circuit 19 that multiplies the input signal of the delay circuit 18 and the output delayed signal, and the output signal is an output selected from a switching circuit, an amplification circuit, an attenuation circuit, a waveform shaping circuit, etc. as necessary. The signal is outputted to the measurement display circuit 21 via the circuit 20, and the frequency of occurrence of the amount of discharged charge 1 of the partial discharge pulse, the generation phase relative to the applied voltage, the waveform, etc. are measured or observed.

FIG. 2 is a characteristic diagram showing the relative intensity ratio of the frequency components of the partial discharge pulse and the noise pulse, and is an explanatory diagram of the basis for setting sb, the band frequency of the band amplification circuit, and the delay time of the delay circuit. In the figure, one song #51 indicates the SF/partial discharge pulse in gas, 52 indicates the void discharge pulse, 53 indicates the thyristor commutation noise pulse, and 54 indicates the relative intensity ratio of the frequency components of the partial discharge pulse in oil. , SF, partial discharge in gas, and void discharge are distributed in the frequency range from 50 MHz to 2000 MHz, whereas that of thyristor noise is approximately 1.
It is known that the frequency of a partial discharge pulse in oil generated from an oil-filled electrical appliance is several MHz or less, and that the upper frequency range of the frequency component of a transmission line corona pulse is approximately equal to that of thyristor noise.

Therefore, in the partial discharge measuring device of the present invention, which uses SF, gas-insulated electrical equipment, and solid-insulated electrical equipment as electrical equipment under test, the passband Wb of the partial discharge pulse is 50 MHz to 100,100 O, and the frequency range lower than this is used to block noise. By setting the frequency band, it is possible to block the output of pulsed external noises such as air thyristor noise, power transmission line corona pulses, and oil discharge pulses, as well as continuous external noises such as broadcast radio waves. Specifically, the band amplification circuit 30 in FIG.
0 pass frequency band Wb 5 QMH2~1000MHz
K is set, and the delay time T+1 of delay circuits 12 and 15 is set to 1 to 1, which corresponds to a half wavelength of 15 to 50 MH2.
By setting 6 x 10 seconds (10~30n8)
I can do that.

Figures 6 and 4 are sample diagrams of signal waveforms for explaining the operation of the above-mentioned partial discharge measuring device. The numbers 30.12 are added to N and P to indicate the status, respectively.
etc. use the reference numerals of each circuit in FIG. 1 to represent its output signal waveform.

In FIG. 6, the noise pulse N30 output from the band amplification circuit 60 is delayed by Ta time in the delay circuit 12 to become a delayed pulse N12, and the noise pulse N30 outputted from the band amplification circuit 60 is converted into a delayed pulse N12 by the subtraction circuit 13.
12 is subtracted, resulting in a trapezoidal pulse N13 whose peak value and pulse width have been reduced.The delay pulse N15 is delayed again by Ta time by the delay circuit 15.N15 is subtracted from N13 by the subtraction circuit 16. By replacing two pulses N16VCK with a pulse width 2Td,
In the delay circuit 18, the pulse N18, which is delayed by 2T (one hour and is prevented from being mixed with N16), is converted into the pulse N1 in the multiplier circuit 19.
By multiplying by 6, the signal N16°N18 is erased, and the output signal N19 of the multiplication circuit 19 becomes almost zero.
Noise pulse N30 can be eliminated.

On the other hand, in FIG. 4, a partial discharge pulse P having a frequency component of 50 MHz or higher is amplified by the band amplification circuit 5o.
30 is delayed by Ta time in the delay circuit 12 and is passed to the subtraction circuit 13.
It is converted into two pulse trains P13 by being subtracted by P13, and then converted into three pulse trains P13 by passing through the delay circuit 15 and subtraction circuit 16, and then converted into three pulse trains P13 by the delay circuit 18.
Since the delayed pulse trains P18 and PI3 delayed by one hour pass through the multiplication circuit 19, overlapping pulses are detected from K, and one partial discharge pulse P19 is amplified by the multiplication circuit 19 and output. .Whether the output pulse P19 retains the original waveform of the partial discharge pulse or the pulse width is several n8
If it is difficult to observe or count the waveform using an oscilloscope or the like, the output circuit 20 or the measurement display circuit 21 shapes the waveform into a shape suitable for measurement and observation.

As described above, the partial discharge pulse, which has been amplified by the bandpass amplifier to the operating level Kt of the noise removal circuit 40 with improved 1) SIN ratio, is once converted into a plurality of pulse trains by the phase shift subtraction means 11 and 14). However, the partial discharge pulse is converted back to the original single pulse by the noise canceling means, and the partial discharge pulse can be outputted to the measurement display circuit via the output circuit 20. On the other hand, the band amplifier circuit 300 has a frequency lower than the passing frequency band Wa, and the delay circuit 12,150 has a delay time of 10 to 3.
Noise in which the pulse rise and fall are longer than 0n8 by 9 hours can be eliminated by passing through the noise removal circuit 40.

FIG. 5 is an S/N ratio characteristic curve showing the noise removal effect when the postponement time is 1On8.
is the S/N ratio for the partial discharge pulse. second phase shift subtraction means 11 and 14 and noise cancellation means 17
This shows the output signal of . Assuming that the rise time of thyristor noise is 100n8, an S/N ratio of about 50 dB (300 times) can be obtained on the output side of the noise canceling means.

6 to 8 are explanatory diagrams of one-shot test examples in the embodiment of FIG. 1, FIG. 6 is a configuration diagram of a test circuit, and FIG. The figure shows the displayed waveform of the measurement display circuit. In FIG. 6, a partial discharge measuring device 50 configured as shown in FIG. 1 is connected to a grounded closed container 54 of the specimen 2 filled with a high voltage bus 52, SF of approximately 3A9f, and gas 55. Then, an AC voltage of 12xv is applied to the bus bar 52 from the high voltage power supply 1, a discharge is generated in the middle chamber of the SF6 gas from the protrusion 53 protruding from the surface of the bus bar 52, and the thyristor is activated by the thyristor inverter connected in parallel to the power supply 1. It is configured to inject noise into the test circuit, and the delay time Ta of the partial discharge measuring device is 10
The n8+ passing frequency band was set to 50 to 1000M100O. As shown in FIG. 7, the output pulse of the band amplification circuit 30 has a high frequency of thyristor noise N30 (600 PCs in terms of maximum discharge charge). It was possible. On the other hand, as shown in FIG. 8, the output waveform of the partial discharge measuring device 50 shows that the thyristor noise pulse N20 is reduced to less than 1/10 (equivalent to about 20 PC) compared to N30 in FIG. The SF buried in the gas, the partial discharge pulse in the gas, the maximum discharge charge amount 2
It could be observed as P2O of 00PC.

Based on the above actual sales results, the partial discharge measuring device of the present invention allows
We were able to demonstrate that SF, partial discharge pulses in gas, or void discharge pulses of approximately several tens of pc can be sufficiently detected in an environment where thyristor noise and the like coexist.

In addition, the partial discharge measuring device of the present invention uses a band amplifier circuit as an AC amplifier with an input equivalent internal noise of less than μV using a wide band transistor, and also uses a subtraction circuit made of a wide band operational amplifier, a wide band linear multiplier, etc. It is possible to process the Varnu signal, which is the partial number t of the pulse width number na, at high speed without changing or distorting it, and therefore discharge pulses that occur with high frequency can be measured with extremely high resolution.

〔Effect of the invention〕

As mentioned above, the present invention has a pass frequency band of 50 to 100.
100O band amplification circuit and delay time 10~30n8
a plurality of phase shift subtraction means each comprising a delay circuit and a subtraction circuit for subtracting input/output signals of the delay circuit; a delay circuit having a delay time corresponding to the delay time of the entire phase shift subtraction means; and input/output of the delay circuit. An analog measuring device was constructed that includes a noise canceling means consisting of a multiplication circuit that multiplies signals.

As a result, thyristor noise, oil discharge noise, power transmission line corona pulse broadcast radio waves, etc. that do not contain frequency components exceeding 50 MHz are attenuated or eliminated as external noise, improving the S/N ratio, and eliminating frequency components exceeding 50 MHz. To provide a partial discharge measuring device for SF, gas-insulated equipment, and solid-insulated equipment, which can output a void discharge nozzle including a void discharge nozzle and a partial discharge pulse in SF6 gas to a measurement display circuit as the number of parts to be measured. I can do it. Also,
The pulse resolution is high because the partial discharge pulse with a pulse width number n8 is processed as a signal with the original waveform, and the gate is continuously closed due to high-frequency noise, which was a problem with conventional devices.
A partial discharge measuring device that eliminates the problem that it is impossible to measure partial discharge pulses and has excellent noise blocking performance that can detect partial discharges in continuous, noise-intruding conditions such as broadcast radio waves. can be provided. Furthermore, by making the band amplifier circuit an AC amplifier using broadband transistors with an internal noise level of several μV or less, it is possible to detect weak partial discharge pulses with an input voltage of about 10 μV. It is possible to provide a highly sensitive partial discharge measuring device that can sufficiently detect partial discharge pulses.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the partial discharge measuring device of the present invention, Fig. 2 is a characteristic diagram showing the relative intensity ratio of frequency components of a pulse signal, and Fig. 3 is a noise noise in the device shown in Fig. 1. Figure 4 is a waveform diagram showing the state of pulse attenuation and erasure, Figure 4 is a waveform diagram showing the state of partial discharge pulses, Figure 5 is an SZN ratio characteristic diagram for the device in Figure 1, and Figure 6 is an experimental example. A schematic configuration diagram of a partial discharge test circuit, FIGS. 7 and 8 are waveform diagrams showing experimental results obtained by the test circuit of FIG. 6,
FIG. 9 is a block diagram of a conventional partial discharge test circuit and measuring device. DESCRIPTION OF SYMBOLS 1... High voltage power supply, 2... Test object, 6... Coupling capacitor, 4... Detection impedance, 5, 6.7.
・Logic control discriminator, 8...Partial discharge measuring device, 8A・
... Gate circuit, 10... Input circuit, 30... Bandwidth amplifier circuit, 40... Noise removal circuit, 11, 14...
・Phase shift subtraction means, 12, 15.18...delay circuit, 1
3.1<S... Subtraction circuit, 17... Noise canceling means, 19... Multiplication circuit, 20... Output circuit, 21...
・Measurement display circuit, 50...partial discharge measuring device, Ta・
...delay time, Wb...passing frequency band, N...noise pulse, P...partial discharge pulse frequency (Hz) Fig. 2 FQ1'=lt + Tsuba 7-3
Figure 4 745 Figure 6 Figure 7 [ Figure 8 Figure 9

Claims (1)

[Claims] 1) A partial discharge pulse having an upper limit frequency component exceeding 50 MHz in a charging current flowing through a partial discharge detection terminal provided on the ground potential side of a high-voltage electric device is replaced with noise having a frequency component lower than the above frequency. It is measured by distinguishing from
a band amplification circuit corresponding to the upper limit frequency region of the partial discharge pulse; a delay circuit provided on the output side of the band amplification circuit to delay an input signal by a predetermined time; and an input/output signal of the delay circuit as an input signal. A phase shift subtraction means formed by continuously connecting a plurality of subtraction circuits to each other, a delay circuit provided on the output side thereof and having a delay time corresponding to the delay time of the phase shift subtraction means, and an input/output signal of this delay circuit inputted. 1. A partial discharge measuring device comprising a noise canceling means consisting of a multiplication circuit that generates a signal. 2) In the item described in claim 1, the pass frequency band of the band amplifier circuit is from 50 MHz to 1000 MHz.
z, and the delay times of the delay circuits of the phase shift subtraction means are each set in the range of 10 nS to 30 nS.