CN211293129U - Partial discharge detection device with combined action of alternating current and impulse voltage - Google Patents

Abstract

The utility model discloses a partial discharge detection device with combined action of alternating current and impulse voltage, which comprises a power frequency test transformer, an impulse voltage generator, an isolation ball gap, a measuring impedance, two filters and an oscilloscope; the power frequency test transformer is connected with a test sample, the impulse voltage generator is connected with the test sample through an isolation spherical gap, the test sample is grounded through a measurement impedance, two ends of the measurement impedance are respectively connected with the oscilloscope through the filter, and the lengths of signal lines leading out signals at two ends of the measurement impedance are the same. The utility model discloses on utilizing power frequency voltage and impulse voltage jointly to use the sample, carry out the suppression that disturbs through the difference of measuring the earth connection and measuring partial discharge signal on the impedance, can accurately obtain the partial discharge signal of sample under the effect of power frequency impulse joint voltage. Adopt the utility model discloses the performance is put in the sample office that tests is more accurate.

Description

Partial discharge detection device with combined action of alternating current and impulse voltage

technical field

The utility model relates to a partial discharge testing device, in particular to a partial discharge testing device with the combined action of alternating current and impulse voltage.

Background technique

Gas combination appliances, transformers, etc. are the key power equipment in the power grid. They will suffer from lightning overvoltage during operation. Lightning overvoltage is a natural overvoltage formed in nature. It has the characteristics of high amplitude and steep waveform front. In addition, these devices are also subject to operating overvoltages during operation.

Partial discharge is an important characterization parameter of insulation deterioration. Through the detection of partial discharge, hidden insulation defects can be effectively discovered, and the equipment can be dealt with before breakdown failure occurs, thereby avoiding the impact of equipment accidents on the power grid. The detection of partial discharge under power frequency voltage has been studied for many years, and it has a relatively mature detection technology.

As mentioned above, in the existing partial discharge testing technology, only attention is paid to the partial discharge performance of electrical equipment/systems under the action of power frequency voltage. How to accurately measure the partial discharge signal is an inescapable difficulty in studying the above problems.

SUMMARY OF THE INVENTION

Purpose of the invention: In view of the above problems, the utility model proposes a partial discharge detection device under the combined action of alternating current and impulse voltage, which can accurately extract the partial discharge signal of the test sample under the combined action of alternating current and impulse voltage. The partial discharge characteristics of the test sample can more accurately reflect the insulation performance of the test sample in the actual power system.

Technical scheme: The technical scheme adopted by the utility model is a partial discharge detection device with combined action of alternating current and impulse voltage, the device includes:

a power frequency test transformer, connected to the test sample, for generating a power frequency voltage signal and applying it to the test sample;

an impulse voltage generator, connected to the test sample, for generating an impulse voltage signal and applying it to the test sample;

Measuring impedance, one end is connected to the test sample, and the other end is grounded;

The oscilloscope is connected to both ends of the measurement impedance, and is used for extracting partial discharge signals from both ends of the measurement impedance for differential operation and display.

Optionally, the device further includes: an isolation spherical gap for protecting the surge voltage generator, the isolation spherical gap is connected in series between the test sample and the surge voltage generator.

Wherein, the isolation spherical gap is a controllable spherical gap, and the spherical gap is triggered simultaneously with the spherical gap inside the impulse voltage generator.

Optionally, the device further includes: an isolation resistor for protecting the power frequency test transformer, and the power frequency test transformer is connected to the test sample through the isolation resistor.

Optionally, the device further includes: an overvoltage suppressor for protecting the measurement impedance, the overvoltage suppressor is connected in parallel with the measurement impedance; when the surge voltage exceeds the action threshold of the overvoltage suppressor, the overvoltage suppressor The overvoltage suppressor becomes short-circuited.

The overvoltage suppressor is a varistor type overvoltage suppressor.

Optionally, the device further includes: a high-pass filter, and the measured impedance is connected to the oscilloscope through the high-pass filter. Among them, the length of the signal lines leading out the signals at both ends of the measurement impedance is the same.

Further, the high-pass filter includes a filter 1 and a filter 2, one end of the measurement impedance is connected to one end of the oscilloscope through the filter 1, and the other end of the measurement impedance is connected through the filter 2. Connect to the other end of the oscilloscope. Among them, the length of the signal lines leading out the signals at both ends of the measurement impedance is the same.

Beneficial effects: Compared with the prior art, the advantages of the present utility model are: (1) the partial discharge performance of the test product is tested by the combined action of alternating current and impulse voltage, which can more accurately reflect the insulation performance of the test product; (2) During the detection process, the AC voltage and the impulse voltage are combined to act on the test product. By suppressing the interference of the difference between the measured ground wire and the voltage signal on the measured impedance, the lifting effect of the impulse voltage on the ground potential and various high voltage signals are eliminated. The influence of frequency interference is improved, and the accuracy of partial discharge signal test is improved; (3) isolation resistance and isolation ball gap are used to prevent the mutual influence of power frequency voltage and impulse voltage.

Description of drawings

FIG. 1 is a schematic structural diagram of the partial discharge test detection device according to the present invention.

Detailed ways

The technical solutions of the present utility model will be further described below in conjunction with the accompanying drawings and embodiments.

During the process of the invention, the inventors noticed:

At present, the detection of partial discharge under impulse voltage is still less, and the difficulty of detecting partial discharge under impulse voltage lies in the suppression of interference. Since the impulse voltage generator itself uses ball-gap discharge to generate waveforms, it has a great impact on the accuracy of detection. This also makes it difficult to study the partial discharge characteristics of electrical equipment under impulse voltage.

In the prior art, the impact voltage is usually considered as a separate factor to examine the influence on the reliability of electrical equipment, without realizing that the partial discharge performance of the equipment may also be unexpected under the combined action of the power frequency voltage and the surge voltage. external influence.

Therefore, the existing partial discharge test technology has no relevant research on the problem of power frequency voltage combined with impulse voltage to test the partial discharge performance of power equipment, and because the impulse voltage itself will cause the ground potential to rise and cause various high-frequency interference, it is easy to produce complex Interfering signals, PD signal detection is more complicated in this case.

The partial discharge detection device for the combined action of alternating current and impulse voltage according to the present invention is shown in Figure 1, including:

Power frequency test transformers, isolation resistors, impulse voltage generators, isolation ball gaps, measuring impedances, overvoltage suppressors, filters and oscilloscopes.

The utility model adopts the power frequency test transformer and the impulse voltage generator as the excitation voltage. Among them, the power frequency test transformer is connected to the mains, and can generate power frequency voltage signals with adjustable amplitude, and the impulse voltage generator can generate impulse voltage signals with adjustable amplitude and waveform parameters. A large resistor is connected in series between the power frequency test transformer and the test sample (hereinafter referred to as the test sample) as an isolation resistor to prevent the surge voltage generated by the surge voltage generator from invading the power frequency power supply; between the surge voltage generator and the test sample An isolation ball gap is connected in series to prevent the intrusion of power frequency voltage to the impulse power supply. Specifically, a large resistor is connected in series between the test product and the power frequency test transformer. In this example, a resistance of 50M ohms is used as the isolation resistance, and the isolation resistance is used to prevent the impulse voltage from acting on the test product and also on the power frequency test transformer. resulting in transformer damage. A controllable ball gap is connected in series between the test sample and the impulse voltage generator as an isolation ball gap. The ball gap can be triggered at the same time with the ball gap of the impulse voltage generator to prevent the power frequency voltage from acting on the impulse voltage generator. Prevent damage to the impulse voltage generator. The power frequency and the impulse voltage are combined to act on the test product. The test product can be an oil-paper insulation test model for transformers or a gas insulation test model for gas-insulated combined electrical appliances. The test product can be a transformer or GIS, or other products, and the type is not limited. A 50-ohm resistor is connected in series with the test sample as the measurement impedance for measuring the partial discharge signal. In addition, in order to avoid the impact of the impulse voltage signal on the measurement impedance, an overvoltage suppressor is connected in parallel with the measurement impedance, and the overvoltage suppressor is a varistor type. Overvoltage suppressor, when the voltage exceeds a certain amplitude, it acts as a short circuit, which can prevent excessive voltage from being applied to the measurement impedance and prevent the measurement impedance from being damaged by overvoltage. Obtain the partial discharge signal generated by the test product on the measured impedance, and connect it to the oscilloscope through a high-pass filter; at the same time, a signal is also obtained from the ground wire and connected to the oscilloscope through the high-pass filter. The partial discharge signal can be obtained by differential calculation of the two signals, and the partial discharge signal can be saved and displayed. As shown in Figure 1, two identical high-pass filters, filter 1 and filter 2, can also be used to filter the two-channel signals.

Because the ground potential will rise under the impulse voltage, and the spark effect will also form a discharge at the ground point, which will cause interference to the partial discharge signal. The high-pass filter can use a filter with a cutoff frequency of 800kHz. At the same time, the signal is also drawn at the grounding point, which is also connected to the oscilloscope through the high-pass filter. The length of the signal line leading out the measurement impedance and the grounding point should be the same. The length of the signal lines is the same, so that the difference between the two signals has a suppressing effect on interference. Differential operations are performed on the two signals in the oscilloscope to obtain partial discharge signals.

The working principle of the partial discharge detection device is as follows: the power frequency voltage continues to act on the sample, and when the combined voltage is required, the trigger ball gap inside the impulse voltage generator and the isolation ball gap outside are triggered. At this time, the impulse voltage acts. On the test product, it forms a combined voltage with the power frequency voltage and acts on the test product at the same time. Under the action of the combined voltage, the test product will generate partial discharge. By measuring the difference between the ground wire and the voltage signal on the impedance to suppress the interference, the partial discharge signal of the test product under the action of the power frequency impulse combined voltage can be accurately obtained. In order to prevent the damage to the measurement impedance caused by the surge voltage, an overvoltage suppressor is used in parallel with the measurement impedance. When the surge voltage exceeds the operating threshold of the overvoltage suppressor, the overvoltage suppressor becomes a short-circuit state, which acts on the measurement impedance at this time. The voltage on it will be zero to avoid damage caused by overvoltage. The overvoltage suppressor can be parameterized according to the actual applied voltage. In the actual test detection, each parameter can be flexibly adjusted according to the needs. The parameters of the impulse voltage generator and the test type can be selected according to the needs, and the parameters of the overvoltage suppressor and the filter can be selected according to the actual situation.

Claims (9)

1. A partial discharge detection device with combined action of alternating current and impulse voltage, characterized in that: the device comprises: Power frequency test transformer, connected with the test sample, used to generate power frequency voltage signal and apply it to the test sample; an impulse voltage generator, connected to the test sample, for generating an impulse voltage signal and applying it to the test sample; Measuring impedance, one end is connected to the test sample, and the other end is grounded; The oscilloscope is connected to both ends of the measurement impedance, and is used for extracting partial discharge signals from both ends of the measurement impedance for differential operation and display. 2 . The partial discharge detection device with combined action of alternating current and impulse voltage according to claim 1 , wherein the device further comprises: an isolation spherical gap for protecting the impulse voltage generator, and the isolation spherical gap is connected in series. 3 . between the test sample and the impulse voltage generator. 3 . The partial discharge detection device with combined action of alternating current and impulse voltage according to claim 2 , wherein the isolation spherical gap is a controllable spherical gap, and the spherical gap and the spherical gap inside the impulse voltage generator are triggered simultaneously. 4 . . 4. The partial discharge detection device with combined action of alternating current and impulse voltage according to claim 1, characterized in that: the device further comprises: an isolation resistor for protecting a power frequency test transformer, the power frequency test transformer passing through the isolation resistor Connect to the test sample. 5 . The partial discharge detection device with combined action of alternating current and impulse voltage according to claim 1 , wherein the device further comprises: an overvoltage suppressor for protecting the measurement impedance, the overvoltage suppressor and the The measurement impedances are connected in parallel; when the surge voltage exceeds the action threshold of the overvoltage suppressor, the overvoltage suppressor becomes a short-circuit state. 6 . The partial discharge detection device with combined action of alternating current and impulse voltage according to claim 5 , wherein the overvoltage suppressor is a varistor type overvoltage suppressor. 7 . 7 . The partial discharge detection device with combined action of alternating current and impulse voltage according to claim 1 , wherein the device further comprises: a high-pass filter, and the measurement impedance is connected to the oscilloscope through the high-pass filter. 8 . 8 . The partial discharge detection device with combined action of alternating current and impulse voltage according to claim 7 , wherein the high-pass filter comprises a filter 1 and a filter 2 , and one end of the measured impedance is passed through the filter. 9 . 1 is connected to one end of the oscilloscope, and the other end of the measurement impedance is connected to the other end of the oscilloscope through the filter 2 . 9 . The partial discharge detection device with combined action of alternating current and impulse voltage according to claim 7 or 8 , characterized in that the length of the signal lines leading out the signals at both ends of the measurement impedance is the same. 10 .

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