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solid vs resistance grounding
4

solid vs resistance grounding

solid vs resistance grounding

(OP)
480, 3ph, 3 wire system supplied by generator.  Should generator neutral be solid grounded or resistance grounded ?  If resistance, how is resistor rating determined ?

RE: solid vs resistance grounding

Low voltage generators are usually solidly grounded.Medium voltage generators are usually low resistance grounded or high resistance grounded if unit connected.  

RE: solid vs resistance grounding

It's going to depend on the system being served by the generator and your tolerance for tracking down ground faults versus machine damage from ground faults.

Low resistance grounding at 480 V is not an option.  High resistance grounding will greatly reduce damage from ground faults and reduce arc-flash exposure for workers.  

Solid grounding is the most prevalent method in use now, but high resistance 480V grounding is gaining in approval, at least in the US.  

RE: solid vs resistance grounding

If the generator directly (not through a transformer) supplies line-neutral load the generator must be solidly grounded.  

RE: solid vs resistance grounding

If this is a backup generator, the grounding of the other source may influence your decision.

Alan
----
"It's always fun to do the impossible." - Walt Disney

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