Backflash

An insulator flashover originating from the pole or tower ground across the insulator onto the phase conductor. This can occur during a lightning strike to the overhead shield wire and where the ground impedance is high. It is referred to as a back flashover since it is in the opposite direction of flashovers produced in laboratory tests. The backflash is usually followed by a standard flashover of the insulator with power frequency current that requires a breaker operation to terminate.