抄録
A practical method for constructing a microprocessor-based wide-area protection system which operates in the current differential scheme is proposed for achieving better selectivity, smaller outage areas and faster operation times than conventional distance backup protection as well as for obtaining coordinated and/or integrated operations of primary and backup protections. The system consists of central equipment (CE), terminal equipment (TE) installed at every circuit breaker, time transfer system such as OPS for providing precise timing signals for the simultaneous sampling of currents throughout the power system, and broadband backbone networks and standardized LAN interfaces with measures for logically dedicated communications channels implemented for signal transmissions between CE and TE. A simplified and effective scheme for expanding protection zones after its primary protection operation by manipulating the current data from CTs in the faulty zone is employed for the backup protection. An experimental system employ ing a 155-Mbps ATM (Asynchronous Transfer Mode)-backbone network and Ethernet interfaces is examined using a power system simulator configuring a busbar and a power line, and operates satisfactorily with respect to both primary and backup protection functions in various states of power system faults and telecommunication failures.
