Influence of VFTO Characteristics on Electric Field Distribution of Basin-Type Insulator Using Transient Method

When operating the switch, Vety Fast Transient Over Voltage (VFTO) will occur due to the characteristics of the GIS bus. It seriously threatens the safety of the equipment in the transformer substation, especially the basin-type insulator. When designing the insulation structure of the basin-type insulator, the uniformity of the electric field distribution ought to be considered firstly. In general, the field distribution is always calculated by using peak voltage of the overvoltage as a boundary condition. However, due to the high frequency, amplitude and gradient of VFTO, whether the wave process is considered may influence the results. Therefore, the electric field distribution of GIS, which includes basin-type insulator and shielding ball, was calculated by COMSOL with the transient method proposed in this paper. Results showed that the distortion and enhancement of the electric field appeared comparing with that calculated by the traditional method. The influence rules of VFTO characteristics including wave front length and amplitude on the electric field calculation was investigated. It could conclude that the smaller value of wave front and the higher value of amplitude will make greater distortion and enhancement on electric field strength.