Statistical Transients in Transmission System

A statistical study for the switching processes in transmission and distribution electric systems, including earth return effect, is presented. The frequency dependence for the parameters of the studied system with a homogenous earth return is included as well as the random values for the closing angle of circuit breakers are taken statistically. Expressions for voltage and currents in modal coordinates are deduced. The overall presence number of transients and the average over-voltage are computed for random angles of switching. The effect of length of lines at different voltage levels is evaluated. A profile for the boundaries of either transmission or distribution network is discussed and analyzed. The comparison in the analysis accounts the effect of transposition for the non-transposed lines. The results are considered for the standard values of voltage level, which is varied from 3 kV up to 500 kV.