277v Lighting and HRG Systems

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adamscb

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Forum,

A coworker told me today that he doesn't prefer 277v lighting when it's being fed from a XFMR with a high-resistance ground system. I asked him why and he said that with 277v lighting, you're essentially forcing one phase to ground, and it will set an alarm on the HRG. What's everyone's thoughts on this?

I would think that with 120v lighting the same would happen, but I'm pretty green to the power field.
 
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GoldDigger

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Some types of lighting including linear fluorescents have a significant capacitive coupling between the arc tube and the grounded metal reflector. Whether that carries enough current to trigger a ground fault detector I can't say for sure, but I doubt it.
If the lamp ballasts are connected line to neutral that does not "force" any current to ground. The current goes back to the transformer secondary on the neutral wire whether it is grounded or HRG.
 
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texie

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adamscb said:
Forum,

A coworker told me today that he doesn't prefer 277v lighting when it's being fed from a XFMR with a high-resistance ground system. I asked him why and he said that with 277v lighting, you're essentially forcing one phase to ground, and it will set an alarm on the HRG. What's everyone's thoughts on this?

I would think that with 120v lighting the same would happen, but I'm pretty green to the power field.
Click to expand...

I think the question is moot as line to neutral loads can not be served by an impedance grounded system. See 250.36(3).
 
don_resqcapt19

don_resqcapt19

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You are not permitted to supply line to neutral loads from an HRG system.
250.36 High-Impedance Grounded Neutral Systems. High-impedance grounded neutral systems in which a grounding impedance, usually a resistor, limits the ground-fault current to a low value shall be permitted for 3-phase ac systems of 480 volts to 1000 volts if all the following conditions are met:
(1) The conditions of maintenance and supervision ensure that only qualified persons service the installation.
(2) Ground detectors are installed on the system.
(3) Line-to-neutral loads are not served.
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adamscb

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But I'm in the clear if I use a 480v to 120/240v transformer to feed the lighting loads, am I correct?
 
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adamscb

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ron said:
If you establish a standard solidly grounded secondary with this 480-120/240V transformer , then that segment isn't HRG anymore. And BTW, you can't get 277V from that transformer.:D
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Right, what I'm saying is using 120v lighting instead of 277v. And solidly grounded secondary, do you mean a solidly grounded neutral on the transformer?
 
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