Abstract: The same frequency and phase AC withstand voltage test technology without GIS bus stop can enhance the power supply reliability. Therefore, it has been widely used in the GIS reconstruction and extension project in recent years. The three-phase cylindrical structure is generally adopted in 110 kV GIS devices. During the same frequency and phase test, there may be breakdown risk in the break-down or inter-phase of the three-station disconnecting switch. Hence, it is necessary to analyze the electric field distribution inside the three-station disconnecting switch. In this paper, the finite element method is used to analyze the internal electric field of three-station disconnecting switch in the 110 kV three-phase cylindrical structure during the GIS withstand voltage test. According to the voltage requirement and the corresponding boundary conditions during the actual test, the electric field distribution characteristics at different positions inside the three-station disconnecting switch are demonstrate in the simulation results. The positions with maximum values of electric field under different applying voltage modes are obtained. Furthermore, the influence of internal structure parameters of the three-station disconnecting switch on the distribution of electric field was analyzed. The presented results can provide theoretical and data support for the application of the same frequency phase withstand voltage test technology in 110 kV GIS devices.

Key words: same frequency and phase, three-station disconnecting switch, electric field, finite element method, AC withstand voltage test