Estimation of the expected annual number of flashovers in power distribution lines due to negative and positive lightning

The paper deals with the estimation of the expected annual number of flashovers in overhead power distribution lines due to indirect lightning strokes and aims at extending a procedure previously proposed by the authors, limited to negative downward events, in order to include also positive events. The obtained results show that positive flashes need proper consideration for an improved selection of protection means and countermeasures against flashovers.