Waveform estimation of particle discharge currents in straight 154 kV GIS using electromagnetic wave propagation simulation

The waveform of the discharge current in gas-insulated switchgear (GIS) has not yet been elucidated. If waveform of the actual excitation input current is known, the simulation will fit the experiment for the electro-magnetic (EM) wave. In the present paper, an attempt was made to determine a standard simulated EM wave shape obtained by changing the rise time t_r of the excitation waveform of a Gaussian pulse of 10-150 ps considering the propagation attenuation in the GIS. This comparison was performed in terms of both the transmission rate Tv of the peak-to-peak value V_pp of the EM wave intensity and the transmission rate T_w of the accumulated energy of the EM wave. The simulation used two types of PD sources: a high-voltage conductor-side particle and a tank-side free particle. The simulation revealed that as t_r is shortened, both T_v and T_w decrease. As a result, it was found that a simulated excitation pulse with a rise time of 10-25 ps produced the best fit to the experimentally obtained T_v and T_w when the calculation was made for a straight GIS structure with two epoxy spacers for the two types of PD sources.