scope:

This TGN gives guidance on the considerations, calculations, and proving of instantaneous highimpedance differential protection systems as applied to busbars, transformers, reactors, capacitors, synchronous machines and similar primary plant connections.

Unless stated otherwise, the rms value is implied for all currents and voltages referred to in this TGN.

Target settings for high impedance differential systems of protection for transmission plant are given in TPS 2.6.2. Where these target settings cannot be achieved, guidance given in this TGN on setting ranges should be followed.