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#213466 - 05/12/14 04:14 PM High Voltage Impedance Grounded System  
Yoopersup  Offline
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Joined: Mar 2003
Posts: 822
Michigan
4160 Volts System .
From Transformer to Resistor must Cable must be insulated for system voltage (4160 ). 250.186 (B) 2011 NEC.
Question from load side of Resistor to ground.
Insulated & rated for 4160 also????
Please state code section.
Yoopersup


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#213467 - 05/12/14 05:40 PM Re: High Voltage Impedance Grounded System [Re: Yoopersup]  
Tesla  Offline
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Joined: Jun 2004
Posts: 1,273
Sacramento, CA
You mean a 4,160VAC 3-phase High Impedance transformer?

Isn't this set-up totally fabricated/ spec'd by a NEMA player?

BTW, what's the transform?

4,160VAC is atypical as a primary loop voltage out my way.

So, I'd take it that this is the secondary voltage out of the transformer and that it feeds motor loads.



Tesla

#213468 - 05/12/14 06:13 PM Re: High Voltage Impedance Grounded System [Re: Yoopersup]  
Yoopersup  Offline
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Joined: Mar 2003
Posts: 822
Michigan
13.8 Primary
4160 Secondary.
Resistor added in Field (Not Factory) done all the time.
From XO on Transformer Wire insulated for 4160 to Resistor.
They have From Load of resistor to Ground bare copper.
I feel per 250.186 (B) it must be 4160 insulated to Ground even after resistor . Because its a Neutral going to ground.
250.186 (C).
It doesn't Change from a Neutral just because it goes thur a resister. Yes it then feeds switchgear which feeds 2 large motor loads. Its on the riser I sent you some time back.
I called the Manufacturer of the Resistor Gard & he said he'd get back to me.



#213472 - 05/14/14 02:37 PM Re: High Voltage Impedance Grounded System [Re: Yoopersup]  
Yoopersup  Offline
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Joined: Mar 2003
Posts: 822
Michigan
Talked to Four Electrical Engineers on this.
Answers all over the place.
Two said bare ground wire off resistor to ground OK
One said 600 Volt insulated to ground.
One said 4160 volt (Same as Phase conductors to Ground )
I Personality think 600 volt insulated from load side of resistor to ground be fine.
Any comments ??
This is an Impedance Grounded System per 250.186 NEC.
Becoming more common in Industrial & Mining.


#213473 - 05/15/14 12:13 PM Re: High Voltage Impedance Grounded System [Re: Yoopersup]  
JBD  Offline
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Joined: Jul 2001
Posts: 599
WI, USA
Does it make sense to say: the conductor intentionally connected to ground must be insulated from ground?

IMO, this conductor should be treated the same as any grounding electrode conductor.


#213474 - 05/15/14 01:13 PM Re: High Voltage Impedance Grounded System [Re: Yoopersup]  
Yoopersup  Offline
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Joined: Mar 2003
Posts: 822
Michigan
My point was (U have a Valid point also ) is it a Neutral Conductor to the Resistor & after a Grounding conductor.
Or is it a Neutral conductor to & from the Resistor to ground?

You get my Just???

Another words does it change after the Resistor ?


#213475 - 05/15/14 01:46 PM Re: High Voltage Impedance Grounded System [Re: Yoopersup]  
gfretwell  Online Content


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Joined: Jul 2004
Posts: 9,059
Estero,Fl,usa
It sounds like a Grounding Electrode Conductor to me. This is not intended to carry the unbalanced circuit current (neutral) it is just establishing a ground reference for the separately derived service.


Greg Fretwell

#213476 - 05/15/14 02:52 PM Re: High Voltage Impedance Grounded System [Re: Yoopersup]  
Yoopersup  Offline
Member
Joined: Mar 2003
Posts: 822
Michigan
250.186 Calls it a Neutral & says it must be insulated at least up to the resister same as Phase conductors .(250.186 (B)& (C). I also talked to the Manufacturer (Gard) & he agreeded up to the Resister it MUST be insulated same voltage as Phase conductors. It's after the Resister I get mixed info.


#213477 - 05/15/14 03:03 PM Re: High Voltage Impedance Grounded System [Re: Yoopersup]  
gfretwell  Online Content


Member
Joined: Jul 2004
Posts: 9,059
Estero,Fl,usa
From XO to the resistor I agree, any voltage drop across the resistor will show up on this conductor but on the grounded side, it should stay ground.
You also have the issue with a bare wire on the XO side being unintentionally grounded and shunting out the resistor. (defeating the purpose). It makes perfect sense to insulate that conductor.


Greg Fretwell


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