Modernising the old transmission protection interfaces - integrated bay solutions to conventional plant

This paper reviews the nature and requirements of the vital interfacing for legacy equipment and examines ways in which improvements might be made in the light of higher-level developments. With trip output devices that are suitable for direct initiation of the circuit breaker (CB) trip circuits and with integral trip circuit and trip output supervision, the old-style process level interfacing could be improved and simplified by the arrangement described in this paper. If interposing relays are still required to provide suitably rated contacts for control purposes, they can be back-of panel mounted with the digital control system (DCS) bay control units, but with no other special requirements.