Wind farm grounding systems design regarding the maximum permissible touch & step voltage

Abstract

Nowadays Wind turbines are used over a wide area as they are environmentally favorably means to product energy without emissions and moreover the fuel is wind which is free for use. Wind turbines are often installed in mountainous area where the soil resistivity and isokeraunic level is high. When the soil resistance is high, the potential rise caused by lightning strike to a wind turbine is more remarkable at the wave tail than at the wave front. On the other hand, the potential rise at the wave tail depends on the steady-state grounding resistance. In this condition the steady-state grounding resistance becomes more important than the transient grounding resistance. In this paper a comprehensive steady-state study on grounding system of wind turbines is presented. Different grounding system configuration will be analyzed. At first a single wind turbine ground system will be considered and the configuration which decrease the step voltage, touch voltage and equivalent grounding resistance of wind turbine grounding system more than other will be selected, then simulations expanded to wind farm which their grounding systems connected to each other. Different grounding methods are analyzed using CYMEGRD which is well known grounding system analysis software.