Abstract: In this study, it is shown that the corona effect attenuates and deforms atmospheric over-voltages which are propagated on the transmission lines. This contributes in a beneficial way to minimization of skirting of the insulators and makes it possible to avoid the short circuits from where a good continuity of service. This has been observed for over-voltages under different distances from its point of impact. The line was represented by its equivalent diagram, divided into N identical cells. The corona effect was simulated by a power source placed in parallel with the capacitor line. The load is simulated by 3 elements in parallel, a resistance, an inductance and a capacitor. The point of impact of over-voltage is taken as voltage source. Over-voltage is simulated by a shock wave 1.2/50 �s represented by an Bi-exponential function. Line of 220 Kv, a 60 km long was used. Equations of the propagation and the current leading to 2n+1 differential equations. The solutions of these equations enabled us to plot the representative curves of over-voltage with: 0; 1000;3000; and 7000 m. the method of Runge-Kutta-Verner was used for the resolution of the differential equations.