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#213466 - 05/12/14 01:14 PM High Voltage Impedance Grounded System
Yoopersup Offline
Member
Registered: 03/04/03
Posts: 822
Loc: 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 02:40 PM Re: High Voltage Impedance Grounded System [Re: Yoopersup]
Tesla Offline
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Registered: 06/16/04
Posts: 1273
Loc: 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.

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#213468 - 05/12/14 03:13 PM Re: High Voltage Impedance Grounded System [Re: Yoopersup]
Yoopersup Offline
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Registered: 03/04/03
Posts: 822
Loc: 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.

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#213472 - 05/14/14 11:37 AM Re: High Voltage Impedance Grounded System [Re: Yoopersup]
Yoopersup Offline
Member
Registered: 03/04/03
Posts: 822
Loc: 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.
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#213473 - 05/15/14 09:13 AM Re: High Voltage Impedance Grounded System [Re: Yoopersup]
JBD Offline
Member
Registered: 07/12/01
Posts: 599
Loc: 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.
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#213474 - 05/15/14 10:13 AM Re: High Voltage Impedance Grounded System [Re: Yoopersup]
Yoopersup Offline
Member
Registered: 03/04/03
Posts: 822
Loc: 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 ?
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#213475 - 05/15/14 10:46 AM Re: High Voltage Impedance Grounded System [Re: Yoopersup]
gfretwell Offline


Member
Registered: 07/20/04
Posts: 9039
Loc: 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.
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#213476 - 05/15/14 11:52 AM Re: High Voltage Impedance Grounded System [Re: Yoopersup]
Yoopersup Offline
Member
Registered: 03/04/03
Posts: 822
Loc: 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.
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#213477 - 05/15/14 12:03 PM Re: High Voltage Impedance Grounded System [Re: Yoopersup]
gfretwell Offline


Member
Registered: 07/20/04
Posts: 9039
Loc: 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.
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Greg Fretwell
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