Solution to partial discharge test of mutual inductor

Work record:

1. The customer feedback that when the voltage transformer is used for partial discharge, the triple frequency partial discharge is often qualified, and the power frequency partial discharge is unqualified;

2. The voltage transformer is used as the voltage standard on site to correct the displayed voltage, and the power frequency and triple frequency voltage are within the error range;

3. Take a 10kV voltage transformer for partial discharge test. The partial discharge is less than 5pC when the third harmonic frequency is 14.4kV, and the partial discharge is 30~60pC when the power frequency is 14.4kV;

4. The screw of the high voltage line is M10, and the screw hole of the transformer is M8. Start to clamp the high voltage line directly on the screw of the transformer; Finally, two M10 nuts are welded on the screw of the transformer and the high voltage wire is directly screwed onto the screw of the transformer. When the power frequency voltage is 14.4kV, the partial discharge is less than 5pC;

Before improvement:

After improvement:

Analysis&Summary:

1. During the power frequency test, the clamp is directly clamped on the screw of the high-voltage wire and transformer, resulting in the discharge caused by the high-voltage tip;