scope:

This TGN lists the continuous and short-term thermal capability of protection equipment employed on the 400 and 275 kV transmission system and associated plant.

However, the permissible overload capability of protection equipment may well be limited, for example, by its required setting in a given application rather than by its thermal overload capability. The application limitations are not covered in this TGN.

The tabulated information is applicable to protection equipment used at all system voltages. However, some of the considerations made when compiling these tables relate only to the 400 and 275 kV systems.