Overcurrent relay

…During a fault, large currents and high voltages occur, so it is important to remove the fault as quickly as possible to prevent its effects from spreading to other areas. After detecting a fault, a protective relay issues a command to a circuit breaker to shut off the fault, which then isolates the faulted section. Classified by detection principle, there are overcurrent relays, overvoltage relays, power directional relays, distance relays, etc., which utilize the large currents and high voltages that are unique to faults; current differential relays and current phase comparison relays, which compare the magnitude and phase of the currents at both ends of the section to be isolated; frequency relays, which detect frequency anomalies; and hydraulic relays, which detect hydraulic abnormalities in transformers. When the two-end comparison method is used and the terminals are far apart, a communication line is used to send and receive signals between them. …

*Some of the terminology that refers to "overcurrent relay" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…故障中は大電流や高電圧が発生するので，故障を極力速く除去することによりその波及を他に及ぼさないことが重要であり，保護継電器は故障を検出後遮断器に遮断を指令し，遮断器が故障区間を切り離す。検出原理によって分けると，故障時特有の現象である大電流や高電圧を利用する過電流継電器，過電圧継電器，電力方向継電器，距離継電器など，切り離す区間の両端の電流の大きさや位相を比較する電流差動継電器，電流位相比較継電器など，周波数の異常を検出する周波数継電器，変圧器の油圧異常を検出する油圧継電器などとなる。両端比較方式で端子間が遠く離れている場合は，相互に信号を送受する通信回線が使われる。…

※「過電流継電器」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報