What is partial discharge? Why do electrical equipment need partial discharge test?
Partial breakdown of electrical discharges in the insulation of electrical equipment, which can occur near conductors or elsewhere, is called partial discharge.

Due to the small energy in the initial stage of partial discharge, its discharge does not immediately cause insulation breakdown, and the intact insulation between electrodes that has not yet been discharged can still withstand the operating voltage of the equipment. However, under the long-term operating voltage, the insulation damage caused by partial discharge continues to develop, which eventually leads to the occurrence of insulation accidents. For a long time, high-voltage power equipment has used non-voltage and withstand voltage tests to check the insulation condition and prevent the occurrence of insulation breakdown accidents. Although the above test methods can briefly or directly judge the reliability of insulation, the potential defects such as partial discharge are very important. It is difficult to find, and the insulation will be damaged during the withstand voltage test, reducing the service life.
According to my country’s statistics on the damage of transformers of 110KV and below, 50% are caused by the gradual development of partial discharge under the operating voltage. Through the partial discharge test, it is possible to find out whether there is partial discharge, severity and location inside the equipment insulation in time, and take timely measures to prevent problems before they occur. In recent years, the rated voltage of power equipment has been increasing. For large-scale ultra-high voltage power equipment, it is possible to replace the short-time high-voltage withstand voltage test with a long-term partial discharge test.
Relevant regulations stipulate that high-voltage electrical equipment must be tested for partial discharge when leaving the factory, and after the lightning impulse test, etc., the partial discharge test must be carried out again to ensure that the partial discharge of the equipment that leaves the factory is within the qualified range. During the supervision of the transformer factory in the shop, there were indeed a certain number of transformers that could not leave the factory due to excessive partial discharge.
In addition, during the operation of the equipment, due to various reasons, the original partial discharge may be qualified, and it may gradually develop into unqualified, and new partial discharge points may also be generated. Therefore, the regular measurement of the partial discharge of the operating equipment by the operating unit is one of the important means of insulation supervision, and it is also a better method to judge the long-term safe operation of the insulation. When there is an abnormality in the equipment, such as the chromatographic analysis exceeding the attention value, it is more necessary to carry out a partial discharge test to identify the abnormal location and degree.

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GDPD-414H Handheld Partial Discharge Detector (Partial Discharge Meter)

4-channel synchronous data acquisition, 4-channel independent signal conditioning unit
· Red, yellow and blue, indicating the severity of partial discharge
· Can display PRPS and PRPD spectrum, ellipse, discharge rate spectrum
· QT plot, N-T plot, PRPD cumulative plot, ψ-Q-N plot are also displayed
· It can display the amplitude and pulse number of PD signal of each channel