Calculation of Lightning Current Distribution within a Wind Turbine and its Surge Protection

The aim of this study is to provide a numerical approach to evaluate lightning effects on the wind turbines. This is a continuation of the investigation conducted on the wind turbine in Nyuzen in Toyama Prefecture in Japan, which, for a validation reason of the numerical models, was equipped with a measurement system [1]. The previous paper was addressed the question of arose overvoltages in the tower foot on the medium voltage side and what effects it does have on the installed there surge arresters during different lightning events. This place could be considered as the most vulnerable for wind turbines during lightning events, since the surge arresters are not directly designed to handle lightning currents. During this study, the previously developed and validated numerical model in EMTP-ATP is taken and extended to include the electrical part on the low voltage side of the observed wind turbine as well as its external lightning protection system which conducts the lightning current from a rotor blade's tip into the tower base and generates overvoltages into the power system. The investigation is conducted without and with overvoltage protection system for different lightning currents.