This Specification defines The National Grid Company plc's (NGC) technical requirements for cross site communication links for teleprotection

The term cross site link is used to define a connection between equipments within the same substation and on the same earth mat. This includes cross site link requirements for connection of unit protection, protection signalling and intertripping systems to substation communication systems. Functional links only are defined.

The part of the teleprotection system which is covered by this Specification is shown in Figure 1. This Specification covers links within the same substation only.

The overall context of this specification in relation to the complete documentation suite is explained in NGTS 3.24.3.