Potential rise and safety voltages of wind turbine earthing systems under transient conditions

In this paper, results of transient simulations of conventional wind turbine earthing systems are presented. Practical wind turbine earthing system models were developed to account for the additional effects of the above-ground tower structure of the wind turbine and also various enhancements to earthing system. Simulations using 1/5 and 8/20 impulse currents were carried out, and a number of parameters were quantified; these include the earth potential rise and the voltage distributions at ground surface level. In particular, the contribution of mitigating techniques, such as rings, rods and the proposed insulated horizontal conductor enhancement were investigated and quantified. The voltage computations allowed determination of touch voltages for all configurations under fast lightning surge conditions.