| 摘要 |
PROBLEM TO BE SOLVED: To avoid unnecessary output even if exciting inrush current including DC component occurs at the time of incorporating large capacity load into a power system, by discriminating occurrence of an accident, conducting instantaneous tripping if an absolute value is beyond a preset value, and conducting time tripping if the absolute value is not beyond the preset value. SOLUTION: Respective set values are inputted through an external setting input part 16, and a comparative value (set value for discrimination) with |i1|+|i2| is set as a variable Y. A measured value |i1|+|i2|is computed as a variable X, and the magnitude of the computed value X is compared with that of the setting value Y. In the case of X>=Y, a variable T is taken as 0. In the case of X<Y, the variable T is taken as a value proportional to Y-X. Using i1, i2, and its difference current, proportion discrimination is made by a computing part 14 for proportion discrimination to discriminate presence of transformer failure. In case that accident occurrence is discriminated, instantaneous tripping is outputted from a trip output part (instantaneous) 17 if T=0. The time limit tripping of time T is outputted from a trip output part (time limit) 18 if T≠0. |
