For problems of pollution flashover on insulator surface because of poor sealed performance of highvoltage switchgear

the contaminated insulation condition of the post insulator under different conditions is detailedly studied based on 10 kV high-voltage switchgear in this work. Firstly

the leakage current under the actual operating voltage is studied

and the results show that with the increase of contamination severity or humidity level

the leakage current presented exponential growth trends. Secondly

this paper studied the leakage current during the process of increasing voltage

the experimental results show that with the increase of voltage

under the low and middle humidity condition

the first discharge pulse occurred in the negative half-cycle of leakage current. With continuous increase of the voltage

the number of discharge pulses increased sharply

the greater the humidity

the more obvious increase trend. The dry area of pollution layer is not easy to form under high humidity

which make discharge pulses occurring in the positive half-cycle of leakage current developed more quickly. Those discharge channels are less but those paths are long

which is enough to cross the insulator surface. Finally

the peak-to-peak value of the leakage current in a power frequency cycle is regarded as a characterization parameter of contaminated insulation condition.This study built the membership function representing different insulation grades

which is a great characterization of the actual situation.