Ligntning Insulation Coordination for a ±600 kV DC Gas Insulated Cable

To determine the required BIL of a +600 kV dc gas-insulated cable, a probabilistic insulation coordination study was performed. An equation was developed to determine the maximum voltage on the cable as a function of directly connected highly nonlinear surge protective devices (MO). After estimating the distribution of surge voltage magnitudes and shapes which arrive at the line-cable junction, the probability of flashover within the cable was determined. The results, analyzed in terms of mean time between failures, MTBF, verified that a 1300 kV BIL was adequate.