Approach for evaluation of lightning current distribution on wind turbine with numerical model

Wind turbines are increasingly becoming an important source of energy for many power systems worldwide. Reliable and safe operation of the turbines is becoming more and more important. Due to their height and exposed location wind turbines are defined as very exposed structures to lightning. A reliable lightning protection system (LPS) for wind turbines is therefore essential. Designing the overvoltage protection system of a wind turbine the lightning current distribution and overvoltages inside the turbine needs to be analyzed. For this purpose the real structure of a specific standard wind turbine is considered. Based on the geometry and material parameters an equivalent circuit model is developed in EMTP-ATP. Using this model, the current distribution and overvoltages can simply be calculated. In the following paper this model is used to investigate the voltage stresses occurring inside the turbine due to direct lightning strike into a rotor blade. Based on the simulation results different overvoltage concepts for the electrical and IT systems are analyzed including the investigation of the power electronic converter of a full converter wind turbine. Ultimately an overvoltage protection concept is suggested that reduces voltage stresses for the electrical and IT system as well as the power converter according to standard [1].