On the Dynamic Electric Field Distribution of 500kV GIS Basin-type Insulators Under Very Fast Transient Over-voltage

In order to prevent the surface breakdown of the basin-type insulator, it is important to optimize its surface electric field distribution. In this paper, a time-resolved model for simulating the electric field distribution of GIS bus duct was presented based on the finite difference time domain method. The electric field distribution of two typical 500 kV GIS bus ducts including the L-type busbar and T-type busbar were calculated. The electric field oscillation due to the effect of GIS geometry was analyzed under different time to crest voltage waveforms. The electric field strength of different locations on the surface of the basin-type insulators were obtained for the two typical structures. Simulation result shows that, for a 500 kV GIS bus duct, when the rise time of applied voltage is less than 4 ns, the peak value of the surface electric field strength of the basin-type insulator is 1.13 much as large as that of the steady-state case. The electric field strength on the surface of the insulator near the inner conductor is the largest. Under the action of a 50 ns ramp wave, the waveform is almost not oscillating and slowly reaches the steady state value. It is recommended that the dynamic electric field characteristics should be taken into account in the insulation design of GIS basin-type insulators.