Neutral to Ground Connections
Neutral to Ground Connections
(OP)
I have the following system looking for preference on neutral to ground connections and would appreciate your comments.
- 13.8kV system is fed by utility connected to Dyg step down transformer feeding the 480V 3Ph and 1Ph loads.
- The same 13.8 system is connected to a local generator through YgD step down transformer (D on generator side) with 480V generator terminal voltage. No Load on generator.
Preference:
1. Generator neutral (star point LV) connected to unit transformer neutral bus (HV side)then connected to ground bus and ground grid.
2. Separate neutral to ground connection for generator and unit transformer high voltage side.
Thanks.
- 13.8kV system is fed by utility connected to Dyg step down transformer feeding the 480V 3Ph and 1Ph loads.
- The same 13.8 system is connected to a local generator through YgD step down transformer (D on generator side) with 480V generator terminal voltage. No Load on generator.
Preference:
1. Generator neutral (star point LV) connected to unit transformer neutral bus (HV side)then connected to ground bus and ground grid.
2. Separate neutral to ground connection for generator and unit transformer high voltage side.
Thanks.






RE: Neutral to Ground Connections
RE: Neutral to Ground Connections
RE: Neutral to Ground Connections
Bill
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"Why not the best?"
Jimmy Carter
RE: Neutral to Ground Connections
Best practices (and in many locations the code) dictate that this should be a direct connection from each systems' grounded leg to the building grounding system. That would rule out Preference #1, which bonds the generator system to the system ground through the 13.8kV neutral bus.
RE: Neutral to Ground Connections
The system is in US and NEC requirement for grounding of derived source at single location can be met by separate grounding of 13.8/0.48kV Dyg transformer feeding the load.
The question is related to 13.8kV feeder coming from the generator unit transformer. The 480V generator and step up Dyg unit transformer are located side by side so if they can not have a common ground bus then their ground grid should be isolated.
Additional clarifications is much appreciated.
RE: Neutral to Ground Connections
All non-current carrying metal surfaces at "ground" (earth) potential has to be bonded together per IEEE recommendations and NEC code as well. You still need to ground each system separately.
RE: Neutral to Ground Connections
RE: Neutral to Ground Connections
RE: Neutral to Ground Connections
A non-seprately derived system would the share the neutral of two systems at the same voltage and grounded at one point only, serving some common loads.
Why go to a neutral of 13.8KV system for grounding a 480V generator?
RE: Neutral to Ground Connections
RE: Neutral to Ground Connections
OP says Delta is on the gen side and transformer HV side has the neutral (wye). In fact it should be called a step-up transformer.
RE: Neutral to Ground Connections