NG DH 27 PDF

PURPOSE

This design handbook offers guidance to CDUs in the use of disconnector auxiliary contacts in protection schemes for all light current replacement, new build and asset replacement work. It is not intended to direct CDUs to a particular solution.

The scope is primarily in the use of disconnector auxiliary switches to select protection schemes or to isolate tripping.

It does not cover the automatic opening of disconnectors for transformer isolation purposes or disconnectors in AC wiring.

This handbook also intends to clarify areas where National Grid requirements may be unclear.