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What are the partial discharge test procedures?

time:2020/11/19   source:华天电力  reading:619 time

Partial discharge test samples should be pretreated in accordance with relevant regulations: keep the surface of the test sample clean and dry to prevent partial discharge caused by moisture or pollution on the insulating surface; if there is no special requirement, the sample should be at ambient temperature during the test; After the previous mechanical, thermal or electrical action, the test should be carried out for a period of time to reduce the influence of the above factors on the test results.

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First, apply a voltage to the test circuit. If the partial discharge does not appear at a voltage slightly higher than the test voltage of the sample, the test circuit is qualified; if the partial discharge interference level exceeds 50% of the allowable value, the interference source must be found to take measures to Reduce interference levels. Before pressurizing, the instruments in the test loop should be calibrated routinely to determine the scale factor of the test loop when the test product is connected, and to eliminate relevant interference. When the voltage is boosted at the specified speed until the discharge volume reaches a specified value, the voltage at this time is the initial voltage of the partial discharge. After that, the voltage is increased by 10%, and then reduced until the discharge amount is equal to the above specified value, and the corresponding voltage is the extinguishing voltage of the partial discharge.

When measuring, do not allow the applied voltage to exceed the rated withstand voltage of the sample. The parameters that characterize partial discharge are measured at a specific voltage, which may be much higher than the initial voltage of partial discharge. Therefore, it should be kept for a certain period of time and be measured multiple times to observe the development trend of partial discharge. You can measure the partial discharge without pre-applied voltage, and then measure the partial discharge after holding for a certain period of time, then reduce the voltage and cut off the power supply. Sometimes the partial discharge can be measured during the voltage increase, decrease or under the specified voltage. It is also possible to measure with pre-applied voltage, after exceeding the specified partial discharge test, increase to the pre-applied voltage, maintain it for a certain time, then drop to the test voltage value, maintain the specified time, and then measure the local area at a given time interval The amount of discharge.

First, set a low-pass filter on the primary of the high-voltage test transformer to suppress interference in the test power supply network. Secondly, the cut-off frequency of the low-pass filter should be as low as possible, and designed to suppress the interference from the phase line and the neutral line. Finally, the isolation transformer should be designed as a shielded structure. Finally, the interference to the partial discharge of the transformer is achieved by suppressing the power supply. This method is mainly applicable to the high-voltage side of the transformer, and the non-halo ring (ball) and the non-halo guide rod are used as the high-voltage connection method.

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