Secondary protection loop system for extra high voltage (EHV) line

The application relates to a secondary protection loop system for an extra high voltage (EHV) line. The secondary protection loop system comprises a circuit breaker operation box and a first fiber distance protection device connected with the circuit breaker operation box. The circuit breaker operation box comprises a blocking autorecloser signal input end for transmitting a blocking autorecloser signal to the outside; and a remote tripping signal input end for transmitting a remote tripping command to the outside. The first fiber distance protection device comprises a start remote tripping leading-in terminal for receiving the remote tripping command transmitted by the circuit breaker operation box. The secondary protection loop system for the EHV line can be used for improving the security and stability of EHV transmission lines.