| 摘要 |
PROBLEM TO BE SOLVED: To improve the protective operation of a protective relay device and to stabilize the power supply to the relay device by preventing the malfunction of a ratio differential relay when a CT is saturated by a zero-point transition current passing through the CT. SOLUTION: Zero-point transition current detecting elements 17 are respectively connected to both end sections of an object to be protected through CTs 12 and the ratio (If0/If1) of a DC component If0 to a fundamental wave component If1 is discriminated at the end sections. When the ratio becomes If0/If1>=1 at either one of the end sections, the occurrence of a zero-point transition current is discriminated and a lock signal is issued to a ratio differential relay 13 so as to prevent the malfunction of the relay 13. |
