According to reports that had been published in many papers, wind turbines (WTs) fault due to
lightning is one of the most difficult challenges. Lightning overvoltage lead to malfunction in the wind farm
equipments. These improper functioning contain of malfunction electronic equipments and deformation of
transformer winding and Surge arrester failures. The travelling waves which are generated due to high
ground potential rise under lightning struck turbine cause these problems. To evaluate these cases, it must
be performed an accurate analysis on the wave shape and level of the Lightning overvoltage and ground
potential rise. This paper investigates the effective factors on the wave shape and level of the overvoltage,
GPR and surge arrester burnout. These factors are included impulse Current-second characteristics,
position of lightning, inception angle, multiple lightning strokes and chopped current. ATP-EMTP simulation
program is applied to analyze the lightning over-voltage of onshore wind farm. This paper provides a
practical procedure of lightning protection.