Design criteria for lightning protection of HV substations

Methods that designers may use to account for substation reliability when adopting insulation coordination strategy are discussed. The choice of criteria is described in terms of the mean time between failures (MTBF). The methods for calculating the MTBF are explored considering several viewpoints: separation and limiting distances, the risk of failure and equipment lifetime, failure rate of substation and system components, substation outage effects, and system outage severity. Procedures for computation of limiting distance and MTBF, including numerical examples, are given