Lightning Protection of the Electrical Systems of WTG: Evaluation Considerations Related to the Application of SPDs

This paper presents a new approach to evaluate the efficiency of surge protective devices (SPD) for the protection against lighting as applied on the electrical power systems of wind turbine generators (WTG). The parameters of the performance of the SPDs which are considered to be critical for this application are their lifetime and voltage protection level at the power input point of the equipment. In this paper a method is presented to determine the lifetime of a SPD component based on the estimation of its exposure to currents due to direct lightning on the WTG over its lifetime using a statistical analysis of the lightning currents that could strike on a WTG and a distribution analysis of the lightning current in the WTG's electrical and grounding system. A lifetime test procedure for SPDs is suggested followed by an experimental verification test. Moreover, the voltage protection level at the equipment power input point is considered and a test procedure is also proposed to measure the effective voltage protection level using several expected voltage and current waveforms. Experimental results are presented to demonstrate the dependence of the voltage protection level on the SPD technology, installation configuration and equipment input impedance. The same approach could also be used in other application areas of SPDs, provided that the corresponding test procedures are adapted to the specific requirements of each application.