Research on Electric Field Distribution and Breakdown Characteristics of GIS Double-fracture Disconnect Switch under Non-outage Experiment

Due to the breakdown of the test-side fracture during the non-outage voltage-withstand test, the double-fracture disconnect switch (DDS) with a common chamber structure has been exposed to the risk of affecting the insulation performance of the operating-side fracture. Therefore, it is necessary to study the electric field distribution and breakdown characteristics of the DSS during the design phase. In this paper, the newly developed 110 kV three-phase common box type GIS DDS was taken as an example. The finite element method was employed to simulate the electric field, as well as to obtain the internal electric field strength distribution during non-outage voltage-withstand test at the actual site. Based on the electric field calculation results and the breakdown criteria deduced by Thomson discharge theory, the breakdown characteristics of the two fractures were studied during non-outage voltage-withstand test. It was proven that the breakdown of the test-side fracture would not affect the insulation performance of the operating-side in the non-outage voltage-withstand testing process of the DDS. The results provide theoretical support for non-outage expansion and on-site insulation test during the second-phase expansion, and also provide a more detailed theoretical basis for insulation verification in the future development of the next-generation DDS equipment.