PROTECTION FOR THYRISTOR CONVERTER

摘要

PURPOSE:To precisely grasp a cause of trouble and to perform a reoperation speedily by a method wherein an abnormal signal is locked during the period when an AC side circuit breaker of a thyristor converter is disconnected or when an AC side current is below the prescribed level. CONSTITUTION:When a circuit breaker 3 is disconnected for some reason by a functioning converter protecting device 9, abnormal signals (c) and (d) are generated by period discriminating circuits 8 and 8' because an AC voltage on a converter 5 is brought to naught. Although there is a possibility of having the circuit breaker 3 to be continuously disconnected even when the cause of trouble has been removed, the circuit 8 is locked so that abnormal signals (c) and (d) will not be generated during a locking signal (e) is applied by means of providing a switch detecting circuit 10 or an undervoltage relay 12, a locking signal (f) is generated before abnormal signals (c) and (d) are generated when the system 2 voltage drops and the circuit 8 is locked. Hence, a converter 5 can be reoperated speedily as occasion demands without stopping its operation.