To prevent fires generated by continuously left on power supply to a house which was destroyed by an earthquake and the like, while taking into consideration the time necessary for escape by providing a sensor for providing a time from the detection of vibration to the operation of a master earth leakage breaker.

A seismoscopic sensor 3, a timer 5, a buzzer 6 and an electromagnetic relay 7 are mounted in a sensor body 1. When the seismoscopic sensor 3 detects the vibration higher than a predetermined magnitude, a signal is transmitted to the timer 5 preset under the consideration of the time necessary for escape, and the timer 5 begins operation. When the preset time has passed, the sense current 8 is sent to a ground leakage breaker to operate the same. When the power is interrupted before the operation of the timer 5, the electromagnetic relay 7 is opened, so that power is not supplied to the house, even if re-energization is applied. The timer 5 operates the buzzer 6 at a set time to generate the warning. That is, since the breaker is cut off after the predetermined time has passed when there is a concern about fire caused by electricity, the fire caused by electricity can be prevented.