  Turning off the supply to a substation is a straightforward affair, as it must be quickly effected in emergencies; the safe removal of metal can follow. The interruption of supply to large areas is easy to those with confidence and little know-how. Irresponsible of me, perhaps, to say even this much.  Turning off the supply to a substation is a straightforward affair, as it must be quickly effected in emergencies; the safe removal of metal can follow. The interruption of supply to large areas is easy to those with confidence and little know-how. Irresponsible of me, perhaps, to say even this much.