- Fast three-phase earthing of the overhead line
The trapped charges will be diverted to earth by the earthing switch. If one of the two methods is successful, the overvoltages due to line energization should be limited to the overvoltage due to earth-fault initiation and clearing. Preinsertion resistors and point-of-wave switching are most suitable to obtain overvoltages in the order 1.5 p.u. Only specially designed surge arresters have protective levels in such low order.