UTILITY CONFIGURATION

[kingpb]

I keep seeing on drawings 3PH, 4W for the utility connection. But, MV (or HV) don't have a neutral conductor, which would be part of a 3PH, 4W system.

Wouldn't this correctly be 3PH 3W +ground?

Secondary Q; the "ground" or earthed conductor at the service entrance from utility just comes from driving a ground rod. I have never seen an actual ground conductor run with the 3 phase conductors.

 

[Joethemechanic]

Well the multi grounded neutral is both a ground and a neutral. And it is connected to the center on wye connected transformers and at other points on some deltas like high leg 120/240 or corner grounds

 

[kingpb]

Well the multi grounded neutral is both a ground and a neutral. And it is connected to the center on wye connected transformers and at other points on some deltas like high leg 120/240 or corner grounds

Yes I would agree this would be the case where a transformer is involved. However, coming off a distribution line that is rated 13.8KV going directly into a lineup of 13.8KV switchgear, no transformer is involved and it's simply 3 phase conductors.

 

[Joethemechanic]

Yes I would agree this would be the case where a transformer is involved. However, coming off a distribution line that is rated 13.8KV going directly into a lineup of 13.8KV switchgear, no transformer is involved and it's simply 3 phase conductors.

I see your point calling a ground conductor a neutral could cause some confusion. Not sure why it's done that way on your drawings.

 

[David Castor]

Uitlity distribution systems are commonly 4-wire with a neutral (often a concentric neutral for underground). Single transformers are usually connected line-to-neutral on the primary side. Most utility distribution circuits carry a neutral conductor, although this is not universal.

 

[Shaneyj]

The Pocos I’m familiar with refer to it as neutral. (Centerpointe, puget sound, Dixie escalante)
If it’s 3ph It’s still 4w regardless what they call it.


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[jim dungar]

Yes I would agree this would be the case where a transformer is involved. However, coming off a distribution line that is rated 13.8KV going directly into a lineup of 13.8KV switchgear, no transformer is involved and it's simply 3 phase conductors.

The source dictates what the system is, not the number of conductors in a circuit.

 

[jaggedben]

I keep seeing on drawings 3PH, 4W for the utility connection. But, MV (or HV) don't have a neutral conductor, which would be part of a 3PH, 4W system.

MV or HV wyes don't exist? 3PH 4W from the utility sounds like a wye or a high-leg delta.

Wouldn't this correctly be 3PH 3W +ground?

Not if 'ground' means an EGC. Utilities don't provide EGCs. But I've heard linemen refer to the neutral as 'ground'. So your term isn't precise.

Secondary Q; the "ground" or earthed conductor at the service entrance from utility just comes from driving a ground rod. I have never seen an actual ground conductor run with the 3 phase conductors.

Again, 'ground' is imprecise. 'Earthed conductor' would be a neutral on a wye or high-leg delta. (I can see an example of the latter out the window across the street right now. They used an insulated neutral but they could have used a bare traveler.) The earthed conductor could also (rarely) be a grounded conductor on a corner grounded delta (which is not a neutral.) But that would be 3W.

Yes I would agree this would be the case where a transformer is involved. However, coming off a distribution line that is rated 13.8KV going directly into a lineup of 13.8KV switchgear, no transformer is involved and it's simply 3 phase conductors.

If it's 3Ph 3W then it's not 3Ph 4W. It could be either, but we can't guess from here what it was agreed that the utility would supply.

 

[kingpb]

The Pocos I’m familiar with refer to it as neutral. (Centerpointe, puget sound, Dixie escalante)
If it’s 3ph It’s still 4w regardless what they call it.


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So physically 4 wires, regardless of what they are used for; i.e. phase and ground.

 

[electrofelon]

So physically 4 wires, regardless of what they are used for; i.e. phase and ground.

Right. For example a transformer served from an MGN system would typically be fed with three concentric 1/3 neutral cables, and the concentrics would be the neutral conductor which would be connected to the primary wye point. For an ungrounded/delta system, the cabling would look the exact same, but the concentrics would just be earthed and connected to equipment cases on both ends.

In both cases the concentrics are part of the cable shielding system (in conjunction with the semicon layer), but in the former they are actually a neutral conductor and carry current. In the latter case they do not carry current (other than induced shield currents) and are more like a bonding or EGC conductor.