Non Standard 3 Phase Services

[texie]

I'm working on a project to teach others about the oddball 3 phase services they may encounter. It would be helpful for others to review for technical accuracy:

Non-Standard 3 Phase Service Types Under 600 Volt.pdf

 

[kwired]

Some people wouldn't call all of them non standard or oddballs:happyyes:

First two you have are pretty common around here.

 

[GoldDigger]

I'm working on a project to teach others about the oddball 3 phase services they may encounter. It would be helpful for others to review for technical accuracy:

Non-Standard 3 Phase Service Types Under 600 Volt.pdf

You are cutting and pasting work documents again Texie.....

And the link shows me an empty Google Doc. It is not empty if I actually download it and view it in Acrobat though.

 

[GoldDigger]

I'm working on a project to teach others about the oddball 3 phase services they may encounter. It would be helpful for others to review for technical accuracy:]

Your last circuit (corner grounded open delta) is workable, but it seems to me that grounding one end of the open delta V rather than the center point of the V is not the best practice.

Is there a particular reason that all of your open delta derivations show the two primaries on A-N and C-N rather than making use of the POCO-supplied wye by running primaries from A-B and B-C? Are both variations found "in the wild"?

It might be better if you explicitly indicate that what you are drawing are the POCO supply transformers and that the primary is some level of MV or HV.

All of your open delta circuits have corresponding full delta circuits, and the interesting features on the secondary side would remain exactly the same.

In your description of the corner grounded delta, you say that all phase-to-phase voltages are 480 (240) and that all phase-to-ground voltages are also 480 (240). That is clearly not true for phase B to ground. When discussing interesting (I will not make any statement about non-standard or oddball) circuits, I think it is important to make sure all of your statements are 100% accurate. Anything else will compromise the goal of your work.

 

[texie]

Some people wouldn't call all of them non standard or oddballs:happyyes:

First two you have are pretty common around here.

Well, yes the 2nd one is pretty common in most parts of the US. The other 3 not so much.

 

[kwired]

Is there a particular reason that all of your open delta derivations show the two primaries on A-N and C-N rather than making use of the POCO-supplied wye by running primaries from A-B and B-C? Are both variations found "in the wild"?

Though you can derive an open delta from all three phase conductors, it is most likely to see them derived from two phases and the neutral. This way POCO can use standard single phase transformers they commonly have to build such systems. And when building an open delta in a remote area you only need to run three primary conductors instead of four to get to the location of the service.

 

[texie]

Though you can derive an open delta from all three phase conductors, it is most likely to see them derived from two phases and the neutral. This way POCO can use standard single phase transformers they commonly have to build such systems. And when building an open delta in a remote area you only need to run three primary conductors instead of four to get to the location of the service.

Yes, that's why I showed it that way. I can tell where you are from.

 

[texie]

Yes, that's why I showed it that way. I can tell where you are from.

I guess I should have said I can tell you have worked in the boonies.

 

[texie]

Your last circuit (corner grounded open delta) is workable, but it seems to me that grounding one end of the open delta V rather than the center point of the V is not the best practice.

Is there a particular reason that all of your open delta derivations show the two primaries on A-N and C-N rather than making use of the POCO-supplied wye by running primaries from A-B and B-C? Are both variations found "in the wild"?

It might be better if you explicitly indicate that what you are drawing are the POCO supply transformers and that the primary is some level of MV or HV.

All of your open delta circuits have corresponding full delta circuits, and the interesting features on the secondary side would remain exactly the same.

In your description of the corner grounded delta, you say that all phase-to-phase voltages are 480 (240) and that all phase-to-ground voltages are also 480 (240). That is clearly not true for phase B to ground. When discussing interesting (I will not make any statement about non-standard or oddball) circuits, I think it is important to make sure all of your statements are 100% accurate. Anything else will compromise the goal of your work.

Yes, I see the error in the last one (corner ground). The ground should be at the V, not the end.

 

[jim dungar]

I do not care for the use of the word 'approximately' when describing the high leg - ground voltage. The correct word is 'nominally'. The math, is the same whether it is 120V and 208V from a center tapped delta or from a center tapped wye.

 

[texie]

I do not care for the use of the word 'approximately' when describing the high leg - ground voltage. The correct word is 'nominally'. The math, is the same whether it is 120V and 208V from a center tapped delta or from a center tapped wye.

Ah, the engineer in you. Point well noted.