| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and system for detection of line-to-ground faults in DC and AC circuits, for facilitating the cost reduction of the whole line-to-ground fault protection system of an AC circuit and a DC circuit in an AC/DC power distribution system. SOLUTION: The method is used for detecting a line-to-ground fault accident of a DC circuit 30 on the basis of a change in excitation current i of a zero-phase transformer 41 for an AC line-to-ground fault. The DC circuit 30 is connected to a secondary-side non-grounding system AC circuit 10 of a main transformer 1. The zero-phase transformer 41 for an AC line-to-ground fault is arranged as an AC line-to-ground fault sensor 40b on the side of the AC circuit 10. A phase current transformer CT1 is installed on the primary side of the zero-phase transformer 41. The phase current transformer CT1 measures a primary-side excitation current of the zero-phase transformer. The change in excitation current i, displaced to the side of the DC circuit when the DC line-to-ground fault accident occurs, is detected by a data arithmetic processing part 81 so as to subject the change to arithmetic processing. COPYRIGHT: (C)2011,JPO&INPIT
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