| 摘要 |
PURPOSE:To enhance the maintenance performance for the double system transmission line and in the case of the transmission line fault, by cutting off the faulty self-station from the transmission line and switching the transmission lines only in the case of the fault of the transmission line itself after the self-diagnosis by the station. CONSTITUTION:Monitor cut-off circuit 26 in transmission/station 6 cuts off relay 21 in case no transmission signal is transmitted within the fixed time and then carries out the self-diagnosis for the transmission part. In case some fault is detected at the transmission part, relay 21 is kept cut off to delete the fault of transmission line 4 due to the fault of the transmission part. While relay 21 is connected again in case the fault is not at the transmission line as the result of the self- diagosis. Counter 27 counts the frequencies of cut-off and connection of relay 21, and the fault of transmission line is decided when the count value exceeds a fixed level of the frequency. Thus, the trigger is applied to register 28, and relay 20 is switched to B of the waiting system from M of the main system. |
