NGR Information Required

We always go for a common neutral earthing resistor and individual neutral earthing breakers or contactors with cross interlocking. The only downside of this is when the resistor/path goes open circuit. For 6 sets you could use duty/standby system for the resistors, assume you will have earth monitoring kit.

Can u send me the elementary Single Line Diagram ( even a hand made sketch) showing major equipment parameters . The reason is that I prefer to get a whole picture of your project, and not look at it through a key-hole.

I understand the economic reasoning for choosing the single-NGR approach, but in my experience the preferred arrangement is the multi-NGR approach, that is, each generator with its own NGR! The principal reasons follow:

1) For safety considerations the common NGR scheme requires that each generator-neutral be disconnectable from the common neutral-bus!

2) For maintenance requirements the common NGR scheme approach should consist of at least two NGRs, so that maintenance can be performed, while the plant is in operation!

3) For operational simplicity the common NGR scheme unduly complicates procedures because whenever a machine is taken out of service, its neutral must be disconnected, either manually or automatically!

I also appreciate that additional engineering is required to provide individual generator-earthing, but in the end, the goal must be to insure personnel safety and simplify operations!

I can provide you with additional details when I have a good picture of the overall design!

I suggest that you use separate NGR for each DG.NGR of the incoming DG set during parallel operation will remain open and closed during running. . But you have to ensure how much circulating current DG set can endure.