Micron-level metal dust is inevitably generated during the opening and closing operation of circuit breaker

which has a significant influence on the internal insulation condition of GIS equipment. The real 363 kV GIS equipment is taken as the foundation in this paper

a test platform for power frequency withstand voltage at 520 kV and lightning impulse withstand voltage at 1 175 kV is set up to carry out the study on the influence of insulation condition of GIS under micron-level foreign matter. First

the study on the distribution of the micro-level foreign matter is developed on the basis of 2 000 times mechanical operation and the variation trend of micron-level foreign matter under different wear numbers of the contact is obtained. Then

the pulse current method is applied for discharge detection under different operation numbers. At the same time

the UHF and ultrasonic partial discharge detection methods are combined to analyze the sensitivity of different detection methods to the micron-level foreign discharge detection. Finally

the artificial embedded method is adopted to study the influence of micron-level metal dust on the insulation performance of GIS

and the insulation margin is checked by the lightning impulse test method and the influence of micro-level foreign matter on the insulation performance of the equipment is obtained.The study of partial discharge detection for different quantities of micron-level foreign objects at different equipment positions in this paper can provide technical support for evaluating the the influence on insulation condition of the equipment during the operation and maintenance period.