JPH03175378A - Measuring apparatus for partial discharge pulse - Google Patents

Abstract

PURPOSE:To measure partial discharge with a high S/N ratio by passing a signal only when a signal having a waveform peculiar to a partial discharge pulse arrives and certainly cutting off pulse like noise. CONSTITUTION:When partial discharge is generated in an insulator 1 tested, potential difference is generated between both terminals of detection impedance 2 and a partial discharge pulse is amplified by an amplifier 5 to be inputted to a multigate circuit 6. When the input pulse satisfies all of the setting conditions of the respective unit gates of the circuit 6, an output signal is applied to a trigger circuit 7 and the output thereof is inputted to a pulse counting apparatus 8. That is, since a YES condition is formed by unit gates (a), (b), (d), (e) and an NO condition is formed by a unit gate (c) and all of the setting signal passes through the circuit 6 and the trigger circuit 7 outputs a trigger signal which is, in turn, measured by the apparatus 8 and the deterioration of the insulator 1 can be diagnosed on the basis of the measured value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a partial discharge pulse measuring device, particularly to a partial discharge pulse measuring device used for diagnosing high voltage electrical insulation.

[Conventional technology]

Partial discharge pulses measured in high-voltage electrical insulation diagnosis are generally weak, so it is important to remove the influence of external noisy pulses, and this affects the sensitivity of partial discharge measurements.

The methods known so far as noise removal methods can be roughly divided into the following four types (IEEJ Technical Report (Part) No. 222r New Measurement Techniques for High Voltage Insulation Characteristics (1988)
(June)).

l) Method of passing only signals of a specific phase of AC applied voltage When AC voltage is applied, partial discharges often occur near or slightly before the positive or negative (or both) peak value. This is used to prevent signals in other phases from passing through the gate.

2) Noise removal using a two-signal differential/balanced detection circuit A bridge circuit is configured with two specimens, and detection is performed using a differential transformer to suppress external noise.

3) Noise removal by multi-signal logic detection circuit This method takes advantage of the fact that there is a certain correlation between the polarity of partial discharge pulses from the specimen and other noisy pulses, and removes noise from electric wires or antennas near the measurement circuit. A signal is received, and the signal passes through the gate only when the polarity of the pulses matches the polarity of the pulse from inside the specimen.

4) Self-phase gate method This method uses the fact that the phase of pulse noise generated from Cyrisk, etc., which is stably generated in synchronization with the power supply frequency, is stable. This method detects the noise one cycle before and uses it to The gate is operated with a one cycle delay to eliminate subsequent noise pulses.

[Problem to be solved by the invention]

However, each of the above methods 1) to 4) has the following drawbacks.

Method l): Although it is true that partial discharge pulses tend to occur concentrated in a specific phase, the phase width varies depending on the conditions, resulting in considerable errors. If the phase width that can pass through the gate is made too narrow, even signal pulses will not pass through.

Method 2): The rate at which noise is removed by the differential circuit depends on the degree of balance between both differential circuits, but it is often difficult to perfectly balance the differential circuits.

It is also necessary to prepare a reference insulator whose conditions closely mirror those of the specimen.

Method 3): In order to reduce malfunctions, it is desirable to increase the number of detection positions, but this is time-consuming and complicates measurement. Furthermore, if the waveform is distorted, it may be difficult to distinguish the polarity.

Method 4): In principle, the first pulse passes through the gate, and as the generated phase gradually shifts, the gate does not operate properly and errors increase.

Therefore, it is an object of the present invention to provide an accurate and sensitive detection system that eliminates errors caused by changes in the generation phase of pulse noise, distortion of waveforms, etc., eliminates the need to use differential circuits that are difficult to balance, and allows easy measurement. The purpose is to enable high partial discharge measurements.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a gate circuit that checks the level of the input signal at a plurality of timings and allows the input signal to pass when the check result satisfies a waveform condition specific to a partial discharge pulse. , provides a partial discharge measuring device.

The gate circuit is constituted by a multi-gate circuit having n pieces (n=2.3, 4, . . . ).

The first gate detects the level of the input signal at time t, the second gate detects the level of the input signal at time t2, and the nth gate detects the level of the input signal at time t7. Each gate checks whether the detected level is within a preset level range (YES condition) or outside the preset level (No condition).

When the YES condition and the No condition are satisfied, the multi-gate circuit allows the input signal to pass through. When the input signal passes through the multi-gate circuit, the passed signal is measured by the measurement circuit. The YES condition and the No condition are set to correspond to a waveform specific to the partial discharge signal. Therefore, the pulse noise signal is blocked by the multi-gate circuit,
Only the partial discharge signal passes through.

〔Example〕

FIG. 1 shows a configuration for performing partial discharge measurement using the partial discharge measuring device according to the present invention. In Figure 1, a detection impedance 2 is connected in series with the insulator under test 1, and a high voltage charging terminal 3
connected between and the earth. At the same time coupling capacitor 4
is connected between the high voltage charging terminal 3 and the ground. The detection impedance 2 is connected to an amplifier 5 , the output of the amplifier 5 is connected to a multi-gate circuit 6 , and the output of the multi-gate circuit 6 is connected to the input of a trigger circuit 7 . The output signal of the trigger circuit 7 is input to a pulse counting device 8. The multi-gate circuit 6 has unit gates a, b, and c.
, d, and e (not shown).

If a partial discharge occurs in the insulator 1 under test when a commercial frequency AC high voltage is applied to the high voltage application terminal 3 , a partial discharge pulse generates a potential difference between both ends of the detection impedance 2 .

This potential difference is amplified by an amplifier 5 and input to a multi-gate circuit 6. When the input pulse satisfies all the setting conditions of each unit gate of the multi-gate circuit 6, an output signal is given to the trigger circuit 7, and the output of the trigger circuit 7 is input to the pulse counting device 8.

In the device of Example 1, the potential range corresponding to the time t1 to t of each unit gate constituting the multi-gate circuit 6 was set as shown in Table 1. In Table 1, time is set to 0 (reference time) when passing through gate e. This setting was made based on the waveform of the partial discharge pulse.

Table 1 An example of a waveform corresponding to the settings in Table 1 is shown in FIG. 2. In FIG. 0, a, b, c, d, and e indicate the set time (relative time) and set potential range of each unit gate.

Assume that the signal input to the multi-gate circuit 6 has the waveform W shown in FIG. This waveform W is a typical partial discharge pulse. As is clear from Figure 2, the unit game)
The YES condition was met for a, b, d, and e, and the NO condition was met for the unit game) c. This means that all the setting conditions are satisfied, and the input signal passes through the multi-gate circuit 6. By this passage, the trigger circuit 7 outputs a trigger signal, and the measuring device 8 measures the trigger signal. Deterioration diagnosis of the insulator 1 under test can be performed based on the count value of the trigger signal.

[Test example]

In order to confirm the improvement in the partial discharge detection sensitivity and the reduction in the misclassification rate according to the present invention, a test was conducted using the configuration shown in FIG. 3.

In FIG. 3, the data recorder 31 is connected to either a level trigger circuit 33 or a multi-gate circuit 34 via a switch 32, and the output side of these is connected to the pulse counter 3.
5.

A magnetic tape on which pulsed noise was recorded was reproduced by a data recorder 31, and the number of pulses passing through either a level trigger circuit 33 or a multi-gate circuit 34 was counted by a pulse counter 35 by selecting a switch 32.

The experimental results were as shown in Table 2. The numerical values in the table are the number of passing pulses counted by the pulse counter 35, that is, the count of pulse noise. According to Table 2, when the sensitivity is 0.13 V and the sensitivity is 0.26 V, when the level trigger circuit is used, 21 and 6 pieces (first test) and 214 and 36 pieces (second test) pulse was detected. 1 and 0 in multi-gate circuits
Only one (first test), two and one (second test) pulses were detected. The level trigger circuit detected pulses even when the sensitivity was set to 0.52 V.

This shows that when multiple gates are used as in the present invention, detected noise is reduced, the S/N ratio is improved, and misclassifications are reduced.

Table 2 [Effects of the Invention] According to the present invention, since the signal is passed only when a signal with a waveform specific to one partial discharge pulse arrives, pulse noise can be reliably blocked. . As a result, partial discharge measurement with a high S/N ratio can be performed.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the configuration used to perform partial discharge measurement in an embodiment of the present invention, and FIG. 2 is an example of a waveform passing through a multi-gate circuit set in an embodiment of the present invention. Shown in Figure 2. FIG. 3 is an explanatory diagram showing a configuration used in a test example of the present invention. Explanation of symbols 1-----1---- Test insulator 2-----1--Detection impedance 3--
−1−−−−−High voltage charging terminal 4−−−−−−−−−−−−−−−1−Coupling capacitor 5−−−・−Amplifier 6−−−−・−・Multi-gate circuit 7−−−− ---Trigger circuit 8--Pulse measuring device 31--Data recorder 32--Switch 33--Level trigger circuit 34--Multi-gate circuit 35・−・−−−−～Pulse counter

Claims (2)

[Claims] (1) A detection impedance that outputs a partial discharge signal corresponding to the level of the partial discharge pulse of the electrical insulator, a gate circuit that allows only a signal having a waveform specific to the partial discharge pulse to pass through, and a signal that has passed through the gate circuit. The measuring circuit includes a measuring circuit for measuring a signal, the gate circuit allows the partial discharge pulse to pass through and blocks a pulse noise signal, and the measuring circuit measures the partial discharge pulse that has passed through the gate circuit. Characteristic partial discharge pulse measuring device. (2) The gate circuit is a multi-gate that checks the level of the input signal at multiple timings and allows the input signal to pass only when the level of the input signal at the multiple timings matches the specific waveform. The measurement circuit includes a trigger circuit that outputs a trigger signal when the multi-gate circuit passes an input signal;
2. The partial discharge pulse measuring device according to claim 1, comprising a pulse counter that counts up when said trigger signal is output.