Switching Surge Insulation Coordination: Lightning Arresters

Methods to determine the protection assured by a lightning arrester with reference to switching surge stress are discussed from a statistical point of view. Two methods are examined: the first considers the lightning arrester as a means to reduce the cumulative frequency of surge distribution, the second considers the arrester as a means to reduce the discharge probability of the insulation to be protected as a function of the prospective value of the applied surge.