| 摘要 |
<P>PROBLEM TO BE SOLVED: To accurately and rapidly judge a ground fault within a protected section regardless of the existence of communication equipment only for a relay. <P>SOLUTION: Breakers 48 and 50 and a protector (C87 relay) are provided in a protected section of a transmissions system using a cable 49 for a transmission line, and the accident of the transmission system is detected by a differential current protective system thereby protecting the transmission line. The C87 relay is provided with a communication device which transfers positive/negative ON-OFF data for judging the existence of a zero-phase current and transmission abnormality, and it calculates the differential current of the above zero-phase current, and also judges the rationality of the above positive or negative ON-OFF data. When the differential current is over a specified value and besides the positive or negative ON-OFF data can be obtained, it sends a switching-off command to the breaker. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
