This paper is devoted to describe how surge magnitudes are calculated and how do we use this data in order to determine the ageing of insulation on the transmission line poles so that we can replace the insulation in pre fault time, based on its condition. The main object of this report is to design algorithm of implementation of SCADA in the transmission line system to identify insulation ageing factor. In order to identify the magnitude of voltage due to direct lightning source, we have some formulae which provides the approximate value. For the magnitude value due to indirect lightning strokes, we use two methods namely RBF-FDTD method which uses artificial neural network function in order to study the detailed concept of coupling between field to transmission lines and the other method is the modelling of simulation system in which the coupling system approximations are taken. This paper also describes about the calculation of outage rate and its Geometrical analysis.