Connecting wye generator to a 480V delta system

[scientist75]

We have the following situation:

1500 kVA delta delta transformer with a 240V secondary 3ph 3W connected to a 5000A 240V bus. We are then feeding a 500 kVA autotransformer (wye connected; 480V secondary) to an automatic transfer switch (3ph 3W). Our customer purchased a 450 kW 480V wye connected generator for a backup generator connected to the ATS. My question is how do I ground the generator?

 

[waross]

How is your delta system grounded? It will ground the generator if it is direct connected. There may be protection issues.

Bill
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"Why not the best?"
Jimmy Carter

 

[scientist75]

The delta system is ungrounded, there is an equipment ground available for bonding at the main service.

 

[waross]

You may float the neutral at the generator. Any grounding method applied to the generator will be applied to the system when on generator power. I would consider high impedance grounding. Also consider high impedance grounding the system and carrying that ground through to the generator.

Bill
--------------------
"Why not the best?"
Jimmy Carter