JPH0524466B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to high voltage equipment such as gas insulated hermetic switchgear (hereinafter abbreviated as GIS), high voltage substation equipment such as transformers, high voltage rotating electric machines, and switchboards. The present invention relates to a partial discharge monitoring device for detecting an abnormality in insulation performance.

[Prior art and its problems]

Technical problems with partial discharge monitoring devices for high-voltage equipment include how to easily detect partial discharge pulses generated inside a grounded metal container from outside the metal container, and how to easily detect partial discharge pulses generated inside a grounded metal container, and The problem of how to distinguish between external noise and partial discharge pulses, and how to distinguish between the types of partial discharges in order to know what kind of defect in high-voltage equipment caused the partial discharge pulses. The problem can be raised.

FIG. 9 is a mock diagram of partial discharge pulses and external noise contained in the detection signal from the GIS, and pulses 101 and 102 are SF ₆ generated in the GIS.
This is an internal corona consisting of a gas corona (pulse width of several ns) and a void corona (pulse width of several 10 ns) generated in a fine cavity in a solid insulator such as an insulating spacer. External noise 104 is superimposed. Examples of pulsed external noise 103 include transmission line corona (pulse width of several 100 ns) generated on overhead power transmission lines, and thyristor (commutation) pulses (pulse width of several μs) of inverters, etc.
In addition, when the equipment under test is gas-insulated equipment or solid-insulated equipment, oil-immersed corona (rise of 1 μs or more and pulse width of several μs or more) generated in oil-immersed cables or oil-filled transformers is also considered as external noise. Obstructing corona surveillance. Also, continuous external noise 104
Broadcast radio waves, power station communication carrier waves (several 10
~ several 100KHz), etc. Although the pulse width and waveform differ depending on the type of partial discharge (corona), on the other hand, the detection signal contains external noise whose pulse width etc. are very close to that of the partial discharge pulse. The reality is that it is extremely difficult to distinguish between types of partial discharges.

FIG. 10 is an example of a partial discharge detection circuit that has been commonly used in the past, and shows an example in which a GIS is used as a test device. In the figure, a partial discharge pulse flowing to the ground via the grounding metal part of the GIS, which consists of a metal container 1 containing a high-voltage charging part, a mount 2, and a grounding wire 3, is transmitted to the ground by a logo plate electromagnetically coupled to the grounding wire 3. It is configured to be detected by a ski coil 4 and measured by a partial discharge measuring device 6 via an impedance-matched coaxial cord 5, and while it is possible to detect partial discharge pulses without providing a special measurement terminal on the GIS, the logo Since the tuning frequency is suppressed by the _Ussky coil, it is designed to amplify and measure the frequency components of several 100 KHz in the detection signal. It was not possible to distinguish the types of equal partial discharges based on differences in their pulse widths, etc.

FIG. 11 is a schematic configuration diagram of an improved conventional partial discharge measuring device, which was previously proposed by the inventors of the present application (application number, Japanese Patent Application No. 59-268979).
issue). In the figure, 1 is a metal container for high voltage equipment, such as GIS, which is grounded by a grounding wire 3;
1 is an input circuit such as a matching circuit conductively connected to the sealed container by a measurement cable 5, and 12 is an input circuit in the detection signal.
Bandwidth amplifier that amplifies 50~1000MHz frequency components,
20 is an analog type noise removal circuit, 13 is an output circuit, and 14 is a display for waveform observation. In the case of the figure, the noise removal circuit 20 consists of two phase shift subtraction circuits 21, 22 and a noise cancellation circuit 23, which are connected in series with each other. The noise canceling circuit 2 consists of a delay circuit that outputs a noise signal, and a subtraction circuit that uses the input/output signals of the delay circuit as input signals.
Reference numeral 3 comprises a delay circuit which delays the output signals of the two phase shift subtraction circuits by the sum of the delay times, for example, 20 to 60 ns, and a multiplication circuit which uses the input/output signals of this delay circuit as input signals.

FIG. 12 is a waveform diagram for explaining the function of the partial discharge measuring device configured as shown in FIG. 11, and shows the input/output signal waveforms of the first stage phase shift subtraction circuit 21. . In the figure, 21A is an input signal waveform of the phase shift subtraction circuit 21, in which a partial discharge pulse P21A due to a corona in SF ₆ gas and an external noise N21A such as a thyristor pulse are superimposed and input. 21B is an output waveform of the delay circuit of the phase shift subtraction circuit 21, and output pulses P21B and N21B delayed by the delay circuit Td are output. 21C is the output waveform of the phase shift subtraction circuit 21, and the partial discharge pulse P is formed into two pulse trains by subtracting the waveform N21B from the waveform 21A.
21C and a noise pulse N21C which is divided and attenuated into two trapezoidal pulses are output. In this way, the phase shift subtraction circuit 21 alone has noise removal performance, but in the case of the figure, the output pulse P21C is further divided into a plurality of pulses by the second phase shift subtraction circuit 22, and the noise is eliminated. By determining the overlap with the delayed pulse in the circuit 23,
External noise is almost completely eliminated, and 1
Only individual partial discharge pulses can be output. In a partial discharge measuring device equipped with a noise removal circuit configured as described above, pulsed external noise and continuous noise having a pulse width wider than the delay time Td of the phase shift subtraction circuit are removed in proportion to the time difference between the two. Since attenuation (phase shift subtraction circuit) can be eliminated, for example, when the test equipment is a GIS, a resin molded transformer, or a rotating electric machine, the void corona as an internal corona or the corona in SF ₆ gas can be used as an external noise for thyristor pulses. , the ability to distinguish and measure corona from power transmission lines, corona in oil, etc. can be significantly improved.

FIG. 13 shows an example of the analysis result of the relative intensity ratio of the frequency components of the partial discharge pulse and the thyristor pulse.
Hz, delay time Td of phase shift subtraction circuits 21 and 22 is 10
It can be seen that by setting the time to 30 ns, only the upper limit frequency components of the void discharge pulse and the gas discharge pulse can be detected. However, in partial discharge monitoring equipment that uses GIS or gas-insulated transformers as test equipment, the detected partial discharge pulses are void discharges in the insulating spacer.
There is a demand to distinguish whether it is a partial discharge pulse in SF ₆ gas, and in partial discharge monitoring equipment that uses rotating electric machines or resin molded transformers as test equipment, it is necessary to distinguish between void corona and GIS in coil insulation or mold insulation. Although there is a demand for distinguishing corona in SF ₆ gas as invading external noise, the apparatus configured as shown in FIG. 11 has not been able to satisfy these demands.

[Purpose of the invention]

The present invention was made in view of the above-mentioned situation, and
It is an object of the present invention to provide a partial discharge monitoring device for high voltage equipment that can detect partial discharge pulses such as corona in SF ₆ gas and void corona, distinguishing them from external noise, and can discriminate the types of the partial discharge pulses. .

[Key points of the invention]

The present invention focuses on the fact that partial discharge pulses due to corona in SF ₆ gas and void corona have narrower pulse widths than other external noises, and there is also a difference in pulse width between the two. Detects in a form close to the waveform, and reduces the delay time of the phase shift subtraction circuit by 2
It is switchably formed into two delay time regions of ~4 ns and 10 ~ 30 ns to remove external noise having a pulse width longer than the two delay time regions, respectively;
And when switching from 2 to 4 ns by utilizing the difference in pulse width between corona pulse in SF ₆ gas and void corona pulse,
Only corona in SF ₆ gas, when switching from 10 to 30ns
The corona in _SF6 gas and the void corona are detected, and the partial discharge pulse detected only when the discriminator circuit switches to the 10-30 ns delay time region is the void corona, and the partial discharge pulse is detected in both the 2-4 ns and 10-30 ns delay time regions. The detected partial discharge pulse is determined to be corona in SF ₆ gas, and a notification signal corresponding to the type of partial discharge is generated. When it is desired to distinguish between corona in gas, corona in void, and corona in oil, it is sufficient to form the delay time range to be switchable into three delay time regions. If a delay time of 500 to 1000 ns is added to the above, corona in oil can be determined.

[Embodiments of the invention]

The present invention will be explained below based on examples.

FIG. 1 is a block diagram showing the configuration of a partial discharge monitoring device showing an embodiment of the present invention. In the figure,
11 is an input circuit that is directly connected to two bolts 7 of a grounded metal part of a high-voltage device, such as a metal container of a GIS, by a detection terminal 10 such as an elastic contact; 12 is a band amplification circuit whose band frequency is set to 50 to 1000 MHz; ,
31 and 41 are phase shift subtraction circuits connected in series, 51 is a noise canceling circuit, 30 is a noise removing circuit, 60 is an output circuit consisting of an amplifier circuit 61 and a peak value holding circuit 62, and 63 is a waveform observer and a counter. 70 is a discrimination circuit, and 71 and 72 are indicators for void corona and corona in SF ₆ gas, respectively. Further, the phase shift subtraction circuits 31 and 41 each include two delay circuits 33, 34 and 43, 44 whose delay times are set to, for example, 2 ns and 8 ns, and subtraction circuits 32 and 42, and whose switching is controlled by a switching control section 40. By connecting the two delay circuits by switching circuits 35 and 45,
It is configured so that it can be switched to two types of delay time regions, 2 ns and 10 ns, and the noise canceling circuit 51 similarly has a delay circuit 53 set to 4 ns and 16 ns, which are the sum of the delay times of the phase shift subtracting circuits 31 and 41. ,5
4 and a multiplication circuit 52, and is configured to be switched to two delay time regions of 4 ns and 20 ns by a switching circuit 55.

Figure 2 is an equivalent circuit for high-frequency current of high-voltage equipment to explain the partial discharge pulse detection method in the above-mentioned embodiment, where Lh is the inductance of the high-voltage conductor, Le is the inductance of the grounded metal container, and Ll is the inductance of the grounded metal container. Ground wire, mount inductance,
Ch is the distributed capacitance between the high voltage conductor and the metal container,
Cl is the ground distributed capacitance of the metal container. now,
When a partial discharge 8 occurs in the insulation between the high voltage conductor and the metal container, the partial discharge pulse propagates through the distributed constant circuit shown in the figure and flows toward the ground.
If a pair of detection terminals of the partial discharge monitoring device are connected to any two points between OP in the figure or to any two points between P, Q, and R in the figure, the inductance Ll,
Partial discharge pulses and the like can be detected as potential drops occurring during Le without significantly changing or distorting them.

FIG. 3 is a structural diagram showing the installation status of the partial discharge monitoring device in the above-described embodiment, in which the terminal fitting 10 makes elastic contact with the head of the bolt 7 that fastens the flange portion 1A of the grounded metal container 1 of the high voltage equipment. The main body case 8 and waterproof shield case 9 of a monitoring device equipped with the By using a direct connection type structure that eliminates the measurement cable between This can prevent pulse widths of several nanoseconds.
Corona in SF ₆ gas can be detected as a partial discharge pulse with a pulse width close to the original waveform.

4 and 5 are principle waveform diagrams showing the state of the partial discharge pulse in the embodiment shown in FIG. 1, and FIG. ₄ shows the delay time of the phase shift subtraction circuits 31 and 41 in FIG. 5 shows a state in which the delay time is set to 2 ns, which is approximately equal to the pulse width of the corona pulse PS, and a state in which the delay time is changed to 10 ns, which is approximately equal to the pulse width of the void corona pulse PV. In the figure, the explanation is simplified by representing the pulse waveform as a rectangular wave. In the figure, the waveform 12W is the output waveform of the band amplifier circuit, 31W and 41W are the output waveforms of the phase shift subtraction circuits 31 and 41, and 54W is the output waveform of the delay circuit 54 of the noise cancellation circuit 51.
62W shows the output waveform of the noise canceling circuit 51, and 62W shows the output waveform of the peak value holding circuit 62, respectively.

In FIG. 4, the corona pulse PS in SF ₆ gas is phase shifted and subtracted by a phase shift subtraction circuit 31 for 2 ns to become two pulse trains 31PS, and further phase shifted and subtracted for 2 ns by a phase shift subtraction circuit 41 to become three pulse trains. pulse train 4
1PS, and is multiplied by the pulse train 54P phase-shifted by 4ns in the delay circuit 54, and the noise canceling circuit 51 outputs one amplified corona pulse 51PS in SF ₆ gas, which is then held by an integrating circuit etc. to maintain the peak value. The circuit 62 inputs it to the measuring device and discrimination circuit 70 as a rectangular wave pulse 62PS suitable for visual inspection. On the other hand, the void corona pulse PV is phase shifted and subtracted by 2 ns in the phase shift subtraction circuit 31, thereby converting it into two pulse trains 31 PV of approximately 2 ns width (in the case of an actual partial discharge pulse, the 12th
As already explained in the figure, the peak value of the pulse is attenuated), and hereafter it is converted to 41PV and 54PV in the same way as the corona pulse PS in SF ₆ gas, but 41PV and 5
4PV do not overlap at the same time, they are erased by the multiplication circuit 51.

On the other hand, when the delay time domain is switched to 10 ns, as shown in FIG. Modified pulse 62 PS, 62
PV is output. Therefore, the discrimination circuit 70 is
Each time the delay time region is switched, the input pulses before and after switching are compared, and if a pulse is detected only when Td = 10 ns, the detected pulse is determined to be a void corona and a display signal is output to the display 71, and the Td but
If a pulse is detected in both the 2ns and 10nS delay time regions, it is determined that it is a corona in SF ₆ gas and a display signal is output to the display 72, thereby distinguishing between corona in SF ₆ gas and void corona. can be monitored. If the equipment under test is SF ₆ gas insulated equipment, both coronas are internal partial discharges, and if the equipment under test is solid insulated equipment, void corona is internal partial discharge, and corona in SF ₆ gas is considered external noise. It goes without saying that you will be judged.

FIG. 6 is a block diagram showing a different embodiment of the present invention. In this embodiment, the noise removal circuit is formed of only one phase shift subtraction circuit 31, and the output circuit 60 is provided with a rectifier circuit 64. This embodiment differs from the described embodiment in this respect.

7 and 8 are principle waveform diagrams for explaining the operation of the partial discharge monitoring device configured as shown in FIG. Corona pulse PS and void corona pulse PV in SF ₆ gas when switched to
Figure 8 shows the state where Td is set to 10 ns, and the pulse width of PS is 2 ns.
PV was displayed as a triangular wave with a pulse width of 10 ns.
When the delay time Td is switched to 2 ns, the corona pulse PS in SF ₆ gas is phase shifted and subtracted by the phase shift subtraction circuit 31 as shown in FIG.
It is converted into a pulse train of 31 PS, and the rectifier circuit 64
One pulse 64 is half-wave rectified by
PS is outputted, converted into a pulse 62PS having a pulse width suitable for visualization by a peak value holding circuit 62, and outputted. Also, void corona pulse PV
is converted into a pulse train 31PV whose peak value is attenuated by being phase-shifted and subtracted by the phase-shift subtraction circuit 31, and rectified by the rectifier circuit 64 to form one pulse 64.
It is converted into PV, and its output is blocked by a threshold value set in the peak value holding circuit 62 or the discrimination circuit 70.

On the other hand, when the delay time Td is changed to 10 ns, the corona pulse in SF ₆ gas is generated as shown in Figure 8.
Both PS and void corona pulse PV follow the same process as the pulse PS in FIG. 7, and pulses 62PS and 62PV are output from the peak value holding circuit 62. Therefore, the discrimination circuit 70 can discriminate whether the detected pulse is a corona in SF ₆ gas or a void corona in the same manner as described in the above embodiment.

As described above, according to this embodiment, the configuration of the monitoring device can be simplified, so that partial discharge monitoring of high-voltage equipment in a state where the level of external noise having a frequency component close to the frequency component of the internal corona pulse is not very high is possible. This has the advantage that the device can be provided at low cost.

〔Effect of the invention〕

As described above, the present invention receives the frequency component in the detection signal containing the partial discharge pulse flowing to the earth side through the grounded metal container of high voltage equipment through a band amplifier with a passband width of 50 to 1000 MHz. Noise that includes a phase shift subtraction circuit consisting of a delay circuit formed to be able to switch an input signal into two delay time regions of, for example, 2 to 4 ns and 10 to 30 ns, and a subtraction circuit whose input signal is the input/output signal of this delay circuit. The removal circuit attenuates or eliminates external noise whose pulse width is wider than the time corresponding to the two delay times, and when the switching control section switches the delay time between the two delay time regions, the output partial discharge pulse The configuration is such that a discrimination circuit is provided for discriminating whether the signal has been output in the delay time domain and outputting the notification signal. As a result, it is possible to detect corona pulses and void discharge pulses in SF ₆ gas with upper frequency components in the range of 50 to 1000 MHz without widening the pulse width. To provide a partial discharge monitoring device for high voltage equipment that can remove or erase external noise such as medium corona or broadcast radio waves, and can distinguish and display corona in SF ₆ gas and Voight corona based on the difference in their pulse widths. I can do it. Therefore, if the high-voltage equipment is gas-insulated equipment, it is possible to distinguish between the corona in the SF ₆ gas and the void corona in the insulating spacer, which was previously difficult to monitor, thereby improving monitoring accuracy and making repairs easier. In addition, if the high voltage equipment is solid insulated equipment, the corona in the SF ₆ gas generated in the SF ₆ gas insulated equipment can be removed as external noise. This can contribute to improving monitoring technology for insulation abnormalities in high-voltage equipment.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an equivalent circuit showing the high frequency response of a grounded metal part of high voltage equipment, FIG. 3 is a structural diagram of the device in the embodiment of FIG. 1, and FIG. 4 and 5 are principle waveform diagrams showing the state of the partial discharge pulse in the embodiment of FIG. 1, FIG. 6 is a block diagram showing a different embodiment of the present invention, and FIGS. Figure 6 is a principle waveform diagram showing the state of the partial discharge pulse in the embodiment, Figure 9 is a superimposed waveform diagram of the detection signal, and Figure 10 is a diagram of the superimposed waveform of the detection signal.
An explanatory diagram of a conventional detection method using GIS as a test device, Fig. 11 is a block diagram of an improved conventional partial discharge measuring device, Fig. 12 is a pulse waveform diagram of the conventional device shown in Fig. 11, and Fig. 13 is a relative intensity ratio diagram of frequency components such as partial discharge pulses. 1... Metal container, 2... Frame, 3... Grounding wire,
7... Volt, 10... Detection terminal, 8... Body case, 9... Shield case, 11... Input circuit, 12... Bandwidth amplifier circuit, 20, 30... Noise removal circuit, 21, 22, 31 , 41... Phase shift subtraction circuit, 51... Noise cancellation circuit, 32, 42...
...Subtraction circuit, 33, 34, 43, 44, 53, 5
4... Delay circuit, 35, 45, 55... Switching circuit, 40... Switching control section, 60... Output circuit, 6
2... Peak value holding circuit, 64... Rectifier circuit, 7
0...Discrimination circuit, 71, 72...Display unit, PS...
...SF ₆ gas corona pulse, PV...Void corona pulse.

Claims (1)

[Claims] 1. Band amplification with a frequency band of 50 to 1000 MHz in the detection signal as a pass frequency band through a detection end that detects a partial discharge pulse flowing to the side of a grounded metal container housing a live part of a high-voltage device. circuit, and a noise removal circuit including a phase shift subtraction circuit comprising a delay circuit for delaying the output signal of the band amplification circuit for a predetermined time and a subtraction circuit whose input signal is an input/output signal of the delay circuit. A plurality of cascade-connected phase shift subtraction circuits each including a delay circuit in which the noise removal circuit can be switched to a plurality of delay time regions determined in accordance with the pulse width of the partial discharge pulse, and a switching circuit for each of the delay circuits. a delay circuit provided on the output side of the phase shift subtraction circuit and configured to be switchable to a delay time equal to the sum of the delay times of the plurality of phase shift subtraction circuits; and input/output signals of the delay circuit. and a noise canceling circuit consisting of a multiplier circuit, which receives the output signal of the noise canceling circuit via an output circuit, and determines whether the input signal is switched to one of the plurality of delay time regions to which it is detected. A partial discharge monitoring device for high voltage equipment, comprising a discrimination circuit that discriminates the type of partial discharge pulse and issues a notification signal. 2. In what is stated in claim 1,
1. A partial discharge monitoring device for high voltage equipment, characterized in that the delay time of the phase shift subtraction circuit is switchable between two delay time ranges of 2 to 4 nS and 10 to 30 nS. 3 In what is stated in claim 1,
1. A partial discharge monitoring device for high voltage equipment, characterized in that a detection end is formed so as to be directly connectable between two predetermined points of a grounded metal container including a grounding wire and a pedestal.