Emerg Gen & XFMR to share the HRG. Any Issues?
Emerg Gen & XFMR to share the HRG. Any Issues?
(OP)
I plan to install a 750KVA 2400V-480 Delta-Wye XFMR with a high resistance ground. There will also be a 200KW emergency generator that feeds the emergency panel through an ATS on loss of the 750KVA XFMR power. I have limited space to add an additional HRG and would like to use a single HRG, connect the neutrals from both the generator and the XFMR together, then run through the HRG. I realize there is a safety concern when performing maintenance on either the generator or the transformer that up to 277V to ground could be seen on the neutral if there is a ground fault on the operating power source. I plan to deal with the safety issue with warning labels on the equipment and notes on the drawings and may also add a disconnect to each neutral to isolate during maintenance. Are there any issues/concerns/recommendations with this approach? Thanks in advance






RE: Emerg Gen & XFMR to share the HRG. Any Issues?
With no line to neutral loads, ground the transformer through the HRG device. Connect the generator neutral to the transformer neutral.
If the generator is grounded as well as the transformer, only one ground system may be connected at any time. You will need a transfer switch that b switches the neutral as well as the phase conductors.
Much easier to connect the generator neutral to the transformer neutral and let one HRG device service both the normal and the standby supplies.
Bill
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"Why not the best?"
Jimmy Carter
RE: Emerg Gen & XFMR to share the HRG. Any Issues?
RE: Emerg Gen & XFMR to share the HRG. Any Issues?
I have several times done repairs when the neutral switching failed and left the neutral open while the power was connected.
Consider the main system without the generator installed.
Yes in the event of a ground fault, the neutral will be at 277 Volts. You need signs warning of the possibility of a hot neutral. Under some safety codes you may have to interlock access covers and doors in the same manner that line connections are protected.
When you install the generator I suggest the same level of protection be applied to locations at both the transfer switch and the generator where the neutral conductor and connections may be accessed.
Bill
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"Why not the best?"
Jimmy Carter
RE: Emerg Gen & XFMR to share the HRG. Any Issues?
I will also use a 3 pole ATS as there will be a place other than the 4th pole to land the generator neutral.
Thank you for the comments.
Mike