Microprocessor-based auto synchroniser for the CEGB´s transmission system

The Central Electricity Generating Board which presently owns and controls the 400 kV and 275 kV supergrid system in England and Wales operates a policy at both these voltages of delayed auto-reclosing (DAR) the switchgear equipment in conjunction with check synchronising. This is the procedure whereby a circuit breaker is closed across an already paralleled system. The equipment used for this purpose is provided on a per circuit basis. The Board also operates a policy of having system synchronisers at selected major substations for the purpose of recoupling a split system in the event of a system breakaway or island situation. These devices were installed on a one per substation basis and are switched into a circuit as required. The authors describe how after a review of this policy a new approach using microprocessors was adopted and a device was designed, evaluated and type approved to meet the new requirements and provide flexibility for possible future needs