Gas insulated switchgear (GIS) and gas insulated transmission lines (GIL) are key equipment in the power system

and their reliability directly affects the safety and stability of the power grid. In recent years

multiple insulator flashovers have occurred during commissioning and operation

in which the GIS/GIL have passed the on-site handover withstand voltage test

greatly affecting the reliability of power supply. In this paper

common fault characteristics are obtained through comparative analysis of multiple similar faults

and typical fault conditions and causes are grasped. Then

the experiment is conducted for fault replication in the factory. The results indicate that insulator without defects do not discharge under alternating current (AC) and direct current (DC) voltage. Insulators with defects can withstand AC withstand voltage but discharge under DC voltage (<400kV). The experiment phenomenon is consistent with the on-site fault

verifying that the on-site fault is caused by small defects under the alternating AC and DC voltage. Based on this

prevention and suppression suggestions for this type of fault are further proposed. This study can help to gain a deeper understanding of the cause of on-site faults

improve the intrinsic safety of equipment

and ensure the safe operation and long-term stability of GIS/GIL.