ABSTRACT
Common-cause failures are an important aspect within reliability analysis and describe a condition, where several components share the same source of failure that causes them to fail or become unavailable simultaneously. The lightning strike is one of the most probable common mechanisms that can cause a simultaneous failure of several generating units at the same site, where the most exposed part of the plant is the on-site switchyard. The direct strike of lightning into the switchyard can put it out of the operation and the installed generating units are no longer connected to the power grid. Therefore the main objective of this paper is to present an approach for estimating the probability of a simultaneous failure of several generating units at the same site caused by a lightning strike. The obtained probability is basis for estimating the common-cause failure parameters. Consequently, common-cause failures of several generating units due to a lightning strike are evaluated and implemented into power system reliability analysis. The results show, that the highest the maximal allowed current amplitude at the on-site switchyard is, the smaller the probability of a common-cause failure of the installed generating units is.
