NGR Design for a 6.6-kV Generator

Dear Guest,

1). Max ground fault = 15 A, yes if charging current is neglected (it is small may be around 3 A, depends on generator capacity).

2). Limiting current may be Ok for 10 seconds (please contact the NGR manufacturer for exact value).

3). Neutral CT shal be located between star point and NGR, not between NGR and ground. This CT will detect any fault in generator and their feeder if the generator directly connected to bus without step up transformer. The earth fault is common for back-up protection. The scheme may be using ground diferential relay or as as common ground fault protection.

4). Earth fault relay is installed in GCB panel, signal distribution is depend the requirements which has been decided before.

5). Disconnecting switch is possible to be provided, even some not using it.

For better solution on this matter please read "Protective Relaying Principle and Applications by J. Lewis Blackburn", and discuss with generator vendor for their requirement. Usually generator and NGR is in one package project.

regards,

Continue to follow yr costomer's specification and get the right thing done.Look at the manuals as well to guide u. Do not add anything of yr own that may endanger the installation or the generator.Consult the customer/manufacturer for things u dont understand on the generator and installation.

Patrick Whowha

Try this link: www.i-gard.com. they are the NGR Experts.