| 摘要 |
PROBLEM TO BE SOLVED: To detect accurately a ground insulation resistance of a low-voltage side electric path even in the case of a small-power insulation monitoring signal, by a simple constitution. SOLUTION: A monitoring signal having a frequency different from a commercial frequency is injected into a class B grounding conductor of a transformer 1, and a leakage current flowing back into the class B grounding conductor through the low-voltage side electric path of the transformer and the ground is detected. On the other hand, a commercial component which is a main noise source is extracted from a reference input from the class B grounding conductor based on a class D grounding point of the low-voltage side electric path, and the commercial component is removed (compensated) from the reference input, and thereby a reference signal B which is a reference for DFT operation is extracted highly accurately from the residual reference input. Then, a ground insulation resistance component which is included in a monitoring signal component of the leakage current detected by the DFT operation which is phase-synchronized with the reference signal B, is determined accurately. COPYRIGHT: (C)2010,JPO&INPIT
|
