Paralleled generator neutral current

[bikenut44]

I have an existing 3MW generator running on a 12,470v wye system that is HRG. The 12,470 also feeds a 12,470 -2400 wye-delta transformer (ungrounded secondary). I want to add a 2400V generator to this bus, but also I was going to add a zig-zag grounding transformer to limit the over voltages during ground. The generator was going to be low resistance grounded. My question is - could you have circulating currents if the generator pitches were dissimilar between the 12,470 and the 2400v system?

 

[waross]

Generators don't usually produce a perfect sine wave not matter what the pitch.
You may get some circulating current at no load, but any load tends to cancel the circulating currents and the resulting wave form is a composite of the wave forms of both generators. This will cause some harmonics that may circulate on the neutral.
Rather than a special order zig-zag transformer you may want to consider three 2400 Volt distribution transformers connected in wye:delta. The secondary voltage is unimportant. You have the option of inserting the ground fault current limiting resistor in either the primary wye point to ground connection or inside the secondary delta.

Bill
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"Why not the best?"
Jimmy Carter

 

[bikenut44]

I wanted to minimize any possible issues but I am having a hard time determining the pitch of the existing machine. I guess my question really is, does using either a zig-zag or a wye-delta grounding transformer provide a path for circulating neutral currents with the upstream 12,470v generator when running in parallel with the new 2400v machine?