7. Lightning transients

7.1 Context

Lightning strikes on overhead lines generate very high overvoltages, which propagate along the lines to reach the substations at the ends. To make the risk of equipment failure due to lightning economically acceptable, it is necessary to specify the equipment isolations and determine the protection to be installed on the network (lightning arresters, spark gaps): this is one of the aims of coordinating isolations .

Lightning surges also trigger overhead line insulator strings, degrading quality of service at network delivery...