| 摘要 |
PROBLEM TO BE SOLVED: To prevent unwanted operation of a leakage relay which occurs sometimes in the other transforming chamber, if a grounding fault occurs in the secondary side of a transformer in one transforming chamber, in the case where the secondary sides of the transformers are installed in a plurality of transforming chambers, such as a high-rise building. SOLUTION: A neutral point-to-ground voltage detecting means 10 for detecting a voltage Vo across the neutral point and the ground, a means 20 for detecting a class-B grounding resistor voltage Ve, a means 30 for detecting a zero-phase current Io and a leakage relay 40 are provided. A neutral point-to- ground voltage Vn under non fault condition is obtained wit the leakage relay from Vo and Ve values, when a grounding fault is generated for calculating the value of Io/(|Vo|/|Vn|). When this value is less than the setting level, operation is stopped so as to prevent an unwanted operation.
|
