In the differential protection instrument null differential protection instrument which possesses

摘要

PROBLEM TO BE SOLVED: To improve a defect of a state in a technique by providing a differential protective device easy to manufacture, economical, and small in volume while having a means for adjusting the setting of a current and time delay.;SOLUTION: The device has a differential current measuring means (1); a means (7) for adjusting the setting of a threshold of a leakage current; and a processing part (2) having a means (9) for adjusting the time delay. The processing part (2) is connected to the measuring means so as to receive a signal indicating a differential current. The means (7) has a switching means (22) having a contact (21) for selecting at least two positions to select the thresholds for the respective positions, and selecting a minimum or a reduced time delay value for at least one of the positions regardless of initial setting of a time delay setting means.;COPYRIGHT: (C)2005,JPO&NCIPI