This Specification describes the functional and performance requirements for the protection of 400 kV, 275 kV and 132 kV copperwork connections. This Specification covers:

(i) The protection of common connections between two or more plant items, where there is no separating circuit breaker, eg mesh corner.

(ii) The protection of transformer HV and LV connections, or mechanically switched capacitor (MSC) connections, where separate zones of protection from the plant protection are required.

(iii) The protection of stub end connections that are formed as a result of disconnector operations within a copperwork protection zone (eg transformer end or feeder end), where the current transformer secondaries are switched by the operating disconnectors.

This Specification does not apply to the protection of busbars at busbar substations, the protection arrangements for which are specified in NGTS 3.6.3 Busbar Protection.

The requirements for the trip relay resetting scheme are specified in NGTS 3.6.15 Trip Relays and Trip Relay Resetting.