Lightning transient characteristics of cable power collection system in wind power plants

In recent years, frequent accidents due to lightning have occurred in wind power plants, resulting in damages to electrical equipments in the power collection system, especially in the cable power collection system (CPCS) and the nacelle step-up transformer. In this study, electromagnetic transient simulation of lightning overvoltage in a 35 kV CPCS with the nacelle step-up transformer was carried out. Influencing factors including the location of the step-up transformer, the lightning current, the grounding resistance of wind turbine generator (WTG) and distance between WTGs are taken into consideration. The simulation results show that, in the case of 30 Ω grounding resistance for the WTG, the current flowing through the arrester installed at the high voltage winding side of the step-up transformer will reach up to 27.1 kA when subjected to a 200 kA lightning current, which reveals the damage mechanism of arrester blasting. Based on the calculation results, recommended nominal discharge current value for the arrester as well as the optimal lightning overvoltage protection method are proposed here.