This paper represents two methodologies for calculating lightning discharge process, which is the basis for comparing two different software products. The tower surge impedance is deeply related to geometric shapes. However, due to the existence of complex transmission line structures, computing surge impedance is not easy. Besides, due to variety of structures of different shapes and sizes, a general equation encompassing all cases is impossible. In this way, equations obtained from simple geometric shapes, such as cylinders and cones, representing various types of towers, were developed [3]. Tower could be represented as inductance connecting shield wires to ground, constant-impedance transmission line, variable-impedance transmission line, or radiating structure. With adequate approximation, travel time can be represented as t=h/c, where t[s] is time, h[m] is tower height and c[m/s] is speed of light. Many experimental and theoretical studies of tower response have been initiated. Scientists Wagner and Hileman found the transient impedance of a cylinder to an impressed surge at the top of the tower. Sargent and Darveniza noted that a cone has constant transient impedance and derived average impedance of cylinder. Chisholm, Chow and Srivastava found that impedance depends on direction of injection, with vertical injection to cylinders and cones agreeing with and horizontal injection matching experiments using this geometry [3,4]. The analysis of lightning performance is fundamental when designing new lines and for uprating existing lines to higher voltages. There are a number of issues in creation of approximate model of lightning discharge into power line tower; towers have not uniform structure and different dimensions and geometry. This paper describes process of power line’s tower model creation for further modelling using software on electromagnetic transient program. The amplitude of the lightning current and its impact place is one of the main characteristics of the lightning discharge. Traditional remedy of lightning protections (ground wire) do not always protect phase conductors against lightning strikes. When lightning strikes in the grounding cable their performance is heavily dependent on HV tower’s ground resistance. The lightning-proof assessing calculations of lightning’s currents amplitude must be adjusted according to the equivalent resistance of the stroked object (ground wire, badly grounded ground wire or overhead tower).