Evaluation of Overvoltages Stressing Insulating Down-Conductor Systems Due to Direct Lightning Strikes Using ATP-EMTP

Insulating down-conductors are utilized in electrically insulated lightning protection systems, LPS, to safely direct the lightning current to the earth, preventing dangerous sparking to conductive parts of the structure as well as damage caused by the flow of the lightning current. The protection afforded by a down-conductor system utilizing insulating downconductors depends upon the design of the air-termination system, that is, the number and positioning of the air terminals, as well as of the catenary wires. This study presents an evaluation of the overvoltages stressing insulating downconductor systems due to direct lightning strikes using ATPEMTP. Both partially and fully electrically insulated LPS of several designs are examined by considering direct negative first and subsequent lightning strokes. The lightning overvoltages stressing an insulating down-conductor are lower in a partially than a fully insulated LPS. A great reduction of both internal and external overvoltages is observed when the electrically insulated LPS utilizes multiple insulating down-conductors.