PURPOSE: To previously warn the interruption of a power source before it is suddenly broken by an earth leakage breaker to take a countermeasure to the power source interruption.

CONSTITUTION: The yolk 1 of an excess current electromagnetic relay has a secondary coil 5, and its output is passed through an amplifying circuit 6 and a rectifying circuit 7 and compared for whether it is larger than a warming alarm current value set in a current value setting circuit 9 or not in a comparator 8. When the output of the secondary coil 5 is larger than the warming alarm current value, a transistor 11 is ON to operate a relay 12, and an alarm is outputted. Thus, the load state up to a distribution system end part can be monitored, and a power source can be stably supplied.