Back Flashover phenomenon analysis in power transmission substation for insulation coordination

Back Flashover (BFO) is one of the several phenomenon which decreases power transmission lines reliability. It occurs as a result of direct lightning stroke to the tower structure or guard wires and injects wave currents with high amplitude and very high steepness to the phase conductors, injection of these wave currents produce voltages with high amplitude and very high steepness, which in turn cause phase to ground faults in power transmission lines. In order to treat with this phenomenon, it is necessary to analysis its mechanism and effective parameters on its occurring probability. In this paper, the mechanism of phenomenon has been analyzed and effective parameters on its probability of occurring are evaluated. Then several methods in order to decrease this probability are suggested. Finally, related simulations with insulation coordination of a 765 kV transmission substation also have been done and the results have been presented.