Wind turbine generators are frequently subjected to lightning due to their locations and height. So, the performance of wind farm under such events is worthy investigated. This paper studies the surge propagation through wind farm when a lightning hits blade of one of the wind turbines. This study includes the problem of ground potential rise on the surge arrester operation. To carry out such analysis a reliable model of wind turbine is essential. For getting appropriate wind turbine model, a high frequency model of surge arrester protecting the boost transformer is used as well as high frequency model of this transformer is implemented. The impact of surge arrester and transformer model on back flow current-overvoltages are highly investigated in the time domain as well as frequency domain using Fast Fourier Transform (FFT) and considering simple wind farm consisting of two wind turbines. Identification parameters of the low voltage (LV) arrester model are introduced including all voltage values of LV levels. The simulation is carried out using ATP/EMTP and MATLAB software. This study provides accurate modelling of wind farms under transients due to lightning. (6 pages)