| 摘要 |
PROBLEM TO BE SOLVED: To provide a leakage detector accurately detecting leaked current over a wide range, even if B-type ground resistance and a capacitance to ground are high. SOLUTION: The leakage detector has a current transformer 1 for detecting a zero-phase current flowing through a B-type grounding line 10; a current zero cross point detecting circuit 8 for detecting a zero cross point of the zero-phase current; a voltage zero cross point detecting circuit 9 for detecting a zero cross point of a reference voltage; an input device 2 for inputting a ground resistance value; and a microcomputer 5 for calculating a leakage current on the basis of the data. The microcomputer 5 obtains a phase difference between a capacitive leakage current and the reference voltage by calculation using the zero-phase current detection value and the previously inputted B-type ground resistance value as a variable, obtains a phase difference between the zero-phase current and the reference voltage from information about the reference voltage zero cross point and information about zero-phase current zero cross point, and obtains a leakage current by calculation using the zero-phase current detection value, the phase difference in the capacitive leakage current and the phase difference in the zero-phase current which are obtained, as a variable. If the obtained leakage current reaches a sensitivity current, the microcomputer 5 detects that a leakage current is generated. COPYRIGHT: (C)2008,JPO&INPIT
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