Switching schemes will be categorized in accordance with this categorization.
Category 1 – No outage necessary within the substation for either maintenance or fault; e.g. the 1 ½ breaker scheme under maintenance conditions in the circuit breaker area.
Category 2 – Short outage necessary to transfer the load to an alternative circuit for maintenance or fault conditions; e.g. the double busbar scheme with bypass disconnect switch and bus-coupler switch under fault or maintenance conditions in the circuit breaker or busbar area.
Category 3 – Loss of a circuit or section; for example the single busbar with bus section circuit breaker scheme for a fault in the circuit breaker or busbar area. The single feed scheme also comes under category 3 service continuity and for this arrangement the addition of incoming circuit breakers, busbar and transformer circuit breakers does not improve the classification.
Category 4 – Loss of substation; for example the single busbar scheme without bus sectionalization for a fault in the busbar area.