Computation of Transient Voltages on Wind Turbines on Frequency-Dependent Soil Caused by Lightning Strikes

Wind energy is one of the main sources of renewable energy in power grids. In this context, wind turbines (WT) are subjected to lightning strikes due to their height and locations. In order to investigate the lightning performance of the WT, an equivalent circuit of the wind structure is implemented in the ATP software. For this analysis, the transient voltages on the WT located on frequency-dependent and -constant soils are calculated. First, the harmonic grounding impedance is computed for a frequency range from 100 Hz up to 5 MHz and the Ground Potential Rise (GPR) developed for the first and subsequent return strokes are assessed. Besides that, time-domain voltages along the WT generated by the same lightning currents injected at the tip of the blade are computed. Results indicated that the voltages at the injection point (blade) have no expressive impact for both soil models. Nevertheless, the GPR developed at the grounding system of the WT has a pronounced reduction for the high-resistive soil for both lightning currents. These results confirm the importance of considering the frequency-dependent soil in transient analysis.