| 摘要 |
PURPOSE:To prevent a mistrip due to malfunction by empolying two-loop constitution for a backup tripping circuit and outputting a trip command on such condition that oscillation at the (n)th detection point is greater than the 2nd- stage trip value and that at a detection point adjoining to it is greater than a backup warning value. CONSTITUTION:When a detection signal from optional one of oscillation detectors 3a-3h only exceeds an abnormal level, neither a normal tripping circuit 10 nor a backup tripping circuit 11 generates an output. When detection signals from two adjacent oscillation detectors among 3a-3h exceed the warning value and either one attains to the 1st-stage trip value, an AND circuit 13 satisfies its output condition, so the normal tripping circuit 10 sends an output signal to an OR circuit 12 to output a trip command. When either of detection signals from two adjacent oscillation detectors among 3a-3h exceeds a backup warning value and the other signal attains to the 2nd-stage trip value while the normal tripping circuit 10 is not in operation, the AND circuit 15 on the side of the backup tripping circuit 11 sends an output signal to the OR circuit 12 to output the trip command. |
