| 摘要 |
PURPOSE:To confine power interruption within a minimum necessary range by detecting a fault occurring in a range to be covered by a digital relay in which an abnormality is present through a backup digital relay located in the upstream of a power system, and then tripping a circuit breaker. CONSTITUTION:When a fault is present, an abnormality signal is read out from another digital relay 9 which inputs a signal to an input interface 18. If an abnormality is detected in the digital relay 9 based on thus read out abnormality signal, a fault detection signal is read out from the digital relay 9 which provides an input to the input interface 18. If no normal digital relay 8 detect a fault, judgment is made that a fault is present within the protective range of a digital relay 8 in which an abnormality is present, and trip signals are provided to downstream circuit breakers 6-1-6-n which are the objects to be tripped by the digital relays 9-1-9-10 in which abnormality is present. |
