When a fault has happened in an a.c. feeding circuit of a.c. electric railway system, it is protected by distance relays and a.c. deruta I type fault selective relay. Recently, with an increase in the transport capacity, feeding currents from substation have increased and a.c. regenerative rolling stock have also increased for rapid transportation. Under the circumstances, the impedance of loads have become closer to the protective zone of distance relay, so the protective zone of distance relays has now to be reduced. We developed a new distance relay to cover a wide zone for fault currents and a narrow zone for load currents, while fault currents have hardly any such harmonics. This distance relay has been introduced on narrow gauge lines after the expected performance was confirmed in experiments and field tests.