Grounded leg delta??
- Thread starter ccha9219
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Ed MacLaren
Senior Member
Re: Grounded leg delta??
Corner grounding permits ground fault protection for the other two phases.
Ed
[ February 27, 2004, 09:40 AM: Message edited by: Ed MacLaren ]
That is true. It is also called "corner grounded" and is used primarily for supplying large pumps, for instance oil and irrigation well services.
Corner grounding permits ground fault protection for the other two phases.
Ed
[ February 27, 2004, 09:40 AM: Message edited by: Ed MacLaren ]
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: Grounded leg delta??
Ed,
First a comment: the most common application of Grounded B phase systems, in our area, is on 240V systems. Maybe your example should show 240 rather than 480V.
Next a possible argument: should the grounded conductor be white or grey?
Ed,
First a comment: the most common application of Grounded B phase systems, in our area, is on 240V systems. Maybe your example should show 240 rather than 480V.
Next a possible argument: should the grounded conductor be white or grey?
- Location
- Illinois
- Occupation
- retired electrician
Re: Grounded leg delta??
Jim,
Why would the color of the grounded conductor be in question? It is a grounded conductor and 200.6 applies.
Don
Jim,
Why would the color of the grounded conductor be in question? It is a grounded conductor and 200.6 applies.
Don
Ed MacLaren
Senior Member
Re: Grounded leg delta??
With regard to wire colors, I was thinking CEC (Canadian Electrical Code), and I even forgot that we now use green for insulated GECs. What color is required for insulated GECs in the USA?
Also, white/grey is reserved for neutral conductors here. Is that not the case there as well?
Ed
[ February 27, 2004, 01:22 PM: Message edited by: Ed MacLaren ]
Would these 240 volt systems be for building services?
With regard to wire colors, I was thinking CEC (Canadian Electrical Code), and I even forgot that we now use green for insulated GECs. What color is required for insulated GECs in the USA?
Also, white/grey is reserved for neutral conductors here. Is that not the case there as well?
Ed
[ February 27, 2004, 01:22 PM: Message edited by: Ed MacLaren ]
- Location
- Illinois
- Occupation
- retired electrician
Re: Grounded leg delta??
Ed,
White/gray is for grounded conductors in the NEC. The corner grounded system has a grounded conductor and the NEC requires it to be white or gray. The NEC does not specify a color for grounding electrode conductors.
Don
Ed,
White/gray is for grounded conductors in the NEC. The corner grounded system has a grounded conductor and the NEC requires it to be white or gray. The NEC does not specify a color for grounding electrode conductors.
Don
Ed MacLaren
Senior Member
Re: Grounded leg delta??
Don,
What should the correct color coding be, other than white for B phase, for the corner-grounded delta system discussed here?
And, is green acceptable for GECs, per the NEC.
Ed
[ February 27, 2004, 03:40 PM: Message edited by: Ed MacLaren ]
Don,
What should the correct color coding be, other than white for B phase, for the corner-grounded delta system discussed here?
And, is green acceptable for GECs, per the NEC.
Ed
[ February 27, 2004, 03:40 PM: Message edited by: Ed MacLaren ]
Re: Grounded leg delta??
Ccha9219, all grounded systems have some point common to multiple windings or a single winding tapped to ground. Take a single phase service, you have one winding and a common conductor tapped to center of this winding which is then attached to ground, this is the same scenario as what Ed is showing.
Draw Ed's diagram, remove the right hand winding and flatten out (open up to 180 deg) the two remaining windings, in essence this would be the same as every single phase service.
Roger
[ February 27, 2004, 02:47 PM: Message edited by: roger ]
Ccha9219, all grounded systems have some point common to multiple windings or a single winding tapped to ground. Take a single phase service, you have one winding and a common conductor tapped to center of this winding which is then attached to ground, this is the same scenario as what Ed is showing.
Draw Ed's diagram, remove the right hand winding and flatten out (open up to 180 deg) the two remaining windings, in essence this would be the same as every single phase service.
Roger
[ February 27, 2004, 02:47 PM: Message edited by: roger ]
Re: Grounded leg delta??
roger,
I have never had the pleasure of working with this system. What you say makes sence but the part that throws me is you have your grounded coductor tapped fom the same spot as b phase
From the diagam, eveythnig I see says dead short
I guess it's one of those things...don't really know why it works it just does
craig
roger,
I have never had the pleasure of working with this system. What you say makes sence but the part that throws me is you have your grounded coductor tapped fom the same spot as b phase
From the diagam, eveythnig I see says dead short
I guess it's one of those things...don't really know why it works it just does
craig
charlie
Senior Member
- Location
- Indianapolis
Re: Grounded leg delta??
I know this sounds weird but you may ground the secondary of any standard transformer configuration one time and one time only at any location. Those locations could be any phase, the center point of any transformer, the center point of a wye, etc. This means that a bank would work but not meet Code if you had a 120/208 wye configuration and grounded a phase wire.
As bad as that sounds, you are permitted to do that with a 480Y/277 volt secondary if you do not ground the center point and you do not bring out a conductor from the center point as a neutral. This will effectively give you a 480 volt delta configuration.
I know this sounds weird but you may ground the secondary of any standard transformer configuration one time and one time only at any location. Those locations could be any phase, the center point of any transformer, the center point of a wye, etc. This means that a bank would work but not meet Code if you had a 120/208 wye configuration and grounded a phase wire.
As bad as that sounds, you are permitted to do that with a 480Y/277 volt secondary if you do not ground the center point and you do not bring out a conductor from the center point as a neutral. This will effectively give you a 480 volt delta configuration.
- Location
- Illinois
- Occupation
- retired electrician
Re: Grounded leg delta??
Ed,
Don
Ed,
The NEC requires that this conductor to be white or gray as required by 200.6. No other colors are permitted by the NEC for this conductor.
In my opinion green is permitted to be used as a grounding electrode conductor, but some NEC "experts" do not agree. It is my opinion that the only colors that cannot be used for the GEC under the NEC are white or gray.
Don
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