JPH068849B2 - Partial discharge pulse measuring device - Google Patents

Description

The present invention relates to a partial discharge pulse measuring device, and more particularly to a partial discharge pulse measuring device useful for diagnosis of high voltage electrical insulation.

[Conventional technology]

Since the partial discharge pulse measured in the diagnosis of high-voltage electrical insulation is generally weak, it is important how much the influence of the noise pulse from the outside can be removed, which influences the sensitivity of the partial discharge measurement.

The methods that have been known so far are roughly classified into the following four methods (Technical Report of the Institute of Electrical Engineers of Japan (Part II) No. 222 “New Measurement Technology for High Voltage Insulation Characteristics” (June 1986)). )reference).

1) Method of passing only signal of specific phase of AC applied voltage When AC applied, partial discharge mainly occurs near positive or negative (or both) peak values or slightly before that. This is used to prevent signals in other phases from passing through the gate.

2) Noise removal by a differential / balanced detection circuit for 2 signals The external noise is suppressed by configuring a bridge circuit with two test pieces and detecting it using a differential transformer.

3) Noise removal by other signal logic detection circuit It utilizes the fact that there is a certain correlation between the polarities of the partial discharge pulse from the DUT and other noisy pulses. Trust and allow the signal to pass through the gate only when the polarities of those pulses match the polarities of the pulses from within the specimen.

4) Self-phase gate method The pulsed noise from the thyristor, etc., which is generated stably in synchronization with the power supply frequency, utilizes the fact that the generated phase is stable. The gate is operated with a delay of 1 cycle to remove the subsequent noise pulse.

[Problems to be Solved by the Invention]

However, the above methods 1) to 4) have the following drawbacks.

Method 1): It is true that partial discharge pulses tend to occur concentrated in a specific phase, but the phase width differs depending on the conditions, so a considerable error occurs. If the phase width that can pass through the gate is too narrow, the signal pulse will not pass through.

Method 2): The rate of noise removal by the differential circuit depends on the degree of balance of 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 are similar to those of the test piece.

Method 3): In order to reduce malfunction, it is desirable to increase the number of detection positions, but it takes time and the measurement becomes complicated. If the waveform is distorted, it may be difficult to determine the polarity.

Method 4): In principle, the first one pulse passes through the gate. In addition, since the generated phase is gradually shifted, the gate does not operate properly and the error increases.

Therefore, the object of the present invention is to eliminate the error due to the change in the phase of the pulse noise, the distortion of the waveform, etc., and to eliminate the need for using a differential circuit that is difficult to balance. This is to enable high partial discharge measurement.

[Means for Solving the Problems]

To achieve the above object, in the present invention, the detection impedance for outputting a partial discharge signal according to the level of the partial discharge pulse of the electrical insulator, and the level of the output signal from the detection impedance including the partial discharge signal at a plurality of timings. A gate means comprising a multi-gate circuit for passing the output signal when the level of the output signal at a plurality of timings is checked and enters a level of a predetermined width determined based on the specific waveform of the partial discharge pulse; Has a trigger circuit that outputs a trigger signal when an output signal is passed through, and a pulse counter that counts up the count of the trigger signal when the trigger signal is output. A partial discharge pulse measuring device is provided.

The gate means is composed of a multi-gate circuit composed of n (n = 2, 3, 4, ...) Unit gates.

The level of the first gate input signal at time t _1, the level of the second gate input signal at time t _2, n-th gate level of the input signal at time t _n, respectively detected. Each gate checks whether the detected level is within a preset level range (YES condition) or is out of the preset level (NO condition).

When the YES condition and the NO condition are satisfied, the multi-gate circuit passes the input signal. When the input signal passes through the multi-gate circuit, the passed signal is measured by the measuring circuit. The YES condition and the NO condition are set so as to correspond to the waveform peculiar 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 the configuration of a portion for performing partial discharge measurement using the partial discharge measuring apparatus according to the present invention. In Fig. 1, the test impedance 1 and the detection impedance 2 are connected in series, and the high voltage charging terminal 3 is connected.
And is connected between the earth. Coupling capacitor 4 at the same time
Is connected between the high-voltage charging terminal 3 and the ground. The detection impedance 2 is connected to the image width device 5, the output of the amplifier 5 is connected to the multi-gate circuit 6, and the output of the multi-gate circuit 6 is connected to the input of the trigger circuit 7. The output signal of the trigger circuit 7 is input to the pulse counting device 8. The multi-gate circuit 6 includes unit gates a, b,
It is composed of c, d, and e (not shown).

When a commercial-frequency AC high voltage is applied to the high-voltage charging terminal 3, when a partial discharge occurs in the test insulator 1, the partial discharge pulse causes a potential difference across the detection impedance 2. This potential difference is amplified by the amplifier 5 and enters the 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 inputted to the pulse counter 8.

In the device of Example 1, the potential range corresponding to the times t _{1 to} t ₅ of each unit gate constituting the multi-gate circuit 6 was set as shown in Table 1. In Table 1, the time is defined as 0 (reference time) when the gate e passes. This setting was made based on the waveform of the partial discharge pulse.

FIG. 2 shows an example of waveforms corresponding to the settings in Table 1. In the figure, a, b, c, d, and e indicate the set time (relative time) and the set potential range of each unit gate.

It is assumed that the signal input to the multi-gate circuit 6 has the waveform W shown in FIG. This waveform W is of a typical partial discharge pulse. As is clear from FIG. 2, the unit gates a, b, d, and e satisfied the YES condition, and the unit gate c satisfied the NO condition. This means that all the set 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 of the partial discharge detection sensitivity and the reduction of the erroneous discrimination rate according to the present invention, a test was conducted with the configuration shown in FIG.

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

The magnetic tape on which pulse noise was recorded was reproduced by the data recorder 31, and the number of passing pulses was counted by the pulse counter 35 through either the level trigger circuit 33 or the multi-gate circuit 34 by selecting the 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 pulse noise count. According to Table 2, when the sensitivity is 0.13V and the sensitivity is 0.26V,
With the level trigger circuit, 21 and 6 (first
The second test) and 214 and 36 (second test) pulses were detected. The multi-gate circuit detected only 1 and 0 (first test) and 2 and 1 (second test) pulses. The level trigger circuit detected the pulse even when the sensitivity was set to 0.52V. This indicates that when a multi-gate is used as in the present invention, the number of detected nozzles is reduced, the S / N ratio is improved, and erroneous discrimination is reduced.

EFFECTS OF THE INVENTION According to the present invention, the signal is passed only when the signal having the waveform peculiar to the partial discharge pulse arrives.
It is possible to reliably block pulse noise. As a result, partial discharge measurement with a high S / N ratio can be performed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration used for performing partial discharge measurement in one embodiment of the present invention, and FIG. 2 is an example of a waveform passing through a multi-gate circuit set in one embodiment of the present invention. It is a waveform diagram shown. FIG. 3 is an explanatory diagram showing the configuration used in the test example of the present invention. Explanation of code 1 ………… Insulator under test 2 ………… Detection impedance 3 ………… High voltage charging terminal 4 ……… 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 (1)

[Claims] 1. A detection impedance for outputting a partial discharge signal according to a level of a partial discharge pulse of an electric insulator and a level of an output signal from the detection impedance including the partial discharge signal are checked at a plurality of timings, The level of the output signal at the plurality of timings is
Gate means comprising a multi-gate circuit that allows the output signal to pass when a level of a predetermined width determined based on the specific waveform of the partial discharge pulse is reached; and when the gate means passes the output signal A partial discharge pulse measuring device comprising: a trigger circuit that outputs a trigger signal; and a measuring unit that includes a pulse counter that counts up the count of the trigger signal when the trigger signal is output.