Evaluation of the Electric Stress on an Insulating Down-Conductor Caused by Lightning Strikes through ATP-EMTP Simulations

Electrically insulated lightning protection systems, LPS, utilize insulating stand-offs and insulating downconductors to maintain the required separation distance from grounded objects. The equivalent separation distance offered by these insulating components can be determined through comparative tests, such as those suggested in IEC TS 625618:2018, where crossed-conductors air gaps under negative standard lightning impulse voltages are used as reference. However, in service the insulating components of an electrically insulated LPS are stressed by non-standard fast-front overvoltages related to lightning currents. In this study the electric stress experienced by the insulating components of an electrically insulated LPS due to direct lightning strikes has been assessed through ATP-EMTP simulations. For the evaluated electrically insulated LPS critical values of separation distance for air-insulated configurations and of dielectric strength for the insulating down-conductor ensuring withstand against the overvoltages estimated for upper limits of lightning currents have been determined.