DEVICE FOR MONITORING HIGH VOLTAGE INSULATION

摘要

PROBLEM TO BE SOLVED: To reduce cost required for detection of a ground fault current to the utmost. SOLUTION: A high voltage insulation monitoring device having a zero-phase current detector 3 for detecting a load-side zero-phase current of a cable way 2 of a non-grounding system has a grounding wire current detector 5 detecting a grounding wire current made to flow to a grounding wire 4 of a high voltage cable 1 of the cable way 2. The high voltage insulation monitoring device previously obtains a ratio of a value of the grounding wire current to a value of the load-side zero-phase current to be stored while ground fault does not occur in the cable way 2, and subtracts an estimation value of the load-side zero-phase current obtained with the value of the grounding wire current and the ratio at a measuring time point from the value of the load-side zero-phase current at a measuring time point to detect a current value of the ground fault current. COPYRIGHT: (C)2011,JPO&INPIT