In this paper, there are evaluated the power systems transients phenomena which appear at the 380 kV no-loaded line switching. In point of news, the paper presents the modelling and simulation of a no-load three-phase line switching effect in Power System, using PSCAD Program and MathCAD Program. There were obtained the transient recovery voltages (TRV) and the overcurrents (OC) in the 380 kV network and the electrical field (EF), according with the overvoltages (OV) at 380 kV. After that, a comparatively analyze of results is made. The paper presents the Electrical Field values, according to modelled and simulated disturbances. The simulation was performed using the EMTDC/PSCAD software package, in order to obtain the transient overvoltages, the overcurrents and the electrical fields in the transmission line and in the busbars. Also in the paper are presented experiments performed for determination of switching overvoltages at the 400 kV no-load lines switching in a Romanian network. After that, a comparative analysis of results regarding switching overvoltages determined through modelling and experiments is made and conclusions about admissible limits recommended by the CIGRE and IEEE international norms are established.