Historical data analysis of lightning and its relation with the Portuguese Transmission system outages

Lightning caused around 26% of the total number of faults in the Portuguese transmission system in the analysed period. Based on historical data, this study uses incident data from 2001 until 2008 (2157 faults in overhead lines) and lightning data from 2003 until 2008 (around 1.65 million cloud-to-ground flashes). The performance of the lightning monitoring system is analysed and the statistical analysis of the incidents caused by lightning is made. Therefore, several indicators are presented, such as average failure rate per 100 km and the percentage of these faults from the total. In addition, month and hour fault distributions are shown and the overhead lines with the worst performance in terms of lightning are identified. The aim of this analysis is to characterize this type of faults in order to evaluate the impact caused by lightning on an operational level. It will be one of the many inputs of a risk assessment methodology.