| 摘要 |
PROBLEM TO BE SOLVED: To alter the settling of a main protective relay to prevent malfunctions in case of anomaly in a transmission line. SOLUTION: A GPS receiver is installed at each station of an optical PCM current differential relay. If a trouble occurs in a transmission line, a station, for example, B immediately downstream from the point of trouble transmits a transmission frame with the current set to zero of the current information of the station A upstream from the point of trouble with transmission timing by GPS to the downstream side. When the current of the current information of the upstream station A is zero, downstream stations C, D, and E respectively change the settling value of a main protective relay to settling values with the normal load current of the station A taken into account, and change the main protective relay conditions. Thus the functionality of the main protective relay is maintained, without relegating protection to back-up protective relays or the like. If the current of the current information of the received transmission frame is zero, the station A replaces the current zero with current data stored in memory to maintain the functionality of the main protective relay. |
