3 wire connection to 4 wire transformer (WYE-WYE)

[mbk2k3]

Hey guys,

Here is the islanded setup:
I have a 3 phase generator (with a NGR in its neutral) connected to a step-up transformer.
I asked for a DELTA-WYE transformer (delta on the generator side).
However the only available transformers are WYE-WYE.

I suspect I can't just leave the XO on the WYE side facing the generator floating/disconnected can I? I'm imagining issues with load imbalances causing current/voltage imbalances, and harmonics passing through the windings, etc.
I could connect an NGR on the XO of the tx as well, only downside is the the ground fault current would increase by an order of magnitude.
I def. can't solidly ground the XO as that would negate the NGR completely.

Am I missing anything else?

 

[dpc]

If you're not connected to the grid or other sources, you can ground both sides of the transformer. The generator NGR will still limit current. If you are connected to the grid, you can float the gen side wye in the transformer. The generator ground provides a ground reference. It really depends on the overall system configuration. But in a grounded wye - grounded wye transformer, the zero sequence current basically passes through the transformer.

 

[mbk2k3]

@dpc

Wait, you can float a WYE winding / disconnect the X0? I thought this was a no-no.

 

[xnuke]

Here's a previous thread on this: thread238-144681

xnuke
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