How to protect protection systems, theory and demonstrations

A theoretical basis has been presented for the protection of power system equipment, which: (a) is in agreement with Maxwell´s equations: (b) provides a correct description of grounding; and (c) has led to correct measurements in numerous expeditions to GIS and open air substations, without optical fibers or surge arresters. The authors emphasize the correct description of the circuits, the current loops, and their coupling via Z_t and Y_t. The concept of transfer impedance is extended to grounding structures and to equipment cabinets. For most disturbances occurring in HV substations, the transfer impedance of equipment and their cabinets is more important than shielding