PURPOSE: To cope easily with system modification by detecting shortcircuit fault and ground fault based on a shortcircuit current distribution pattern and ground fault current distribution pattern which are prepared on the basis of a shortcircuit current value and a ground fault current value stored in nonvolatile memories.

CONSTITUTION: When shortcircuit current or ground fault current is detected through detecting means arranged in a main line 12 and each branch 14, the detected shortcircuit current value and ground fault current value are stored in nonvoltage memories 21a, 21b. Then a master station throws in main line switches 13a, 13b remotely to transmit power preliminarily on the main line 12, and the shortcircuit current value and the ground current value stored in the nonvolatile memories 21a, 21b are transmitted through poling of the master station. Thereafter, a shortcircuit current distribution pattern and a ground fault current distribution pattern are prepared in the master station and a faulty section is detected based on the patterns, then switches in sound sections are closed remotely through the master station thus separating the faulty section.