In this paper the impulse generator circuit is evaluated by taking capacitance of the 6.35/11 kV, 3-core cable as load by using Matlab Simulink. Cable of same voltage rating i.e. 6.35/11 kV but of different size is taken. Attempts are made to evaluate the variation in the front resistance and tail resistance of the impulse generator for different size of cable, in order to get the standard wave front time and wave tail time. Further the efficiency and voltage regulation is calculated for different size of the underground cable and for different values of C 1 /C 2 .