Utility upgrade from 4.16kv to 13.8kv.

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I'll speculate. Budgetary reasons prevented the utility from doing the additional work. Purely speculation on my part.:thumbsup:
 
peter d said:
They could, but they would much rather take a delta system out of service, than replace it.
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My preference, if I had a desire to get rid of them, would be to phase them out by not offering them to new customers. I really don't see why allowing them for existing is a big deal. I can get pretty much any standard transformer I need in short order and units for delta banks are pretty standard.
 
chris1971 said:
We could speculate all day and never have the answer.:thumbsup:
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My speculation is you eat an elephant one bite at a time. You simply can't do everything at once. I would anticipate the tap to eventually be upgraded. That's the way we have done it for many utilities, especially the larger ones.
 
mivey said:
If they are one of those wanting to get rid of delta banks. Too much ado about too little IMO.
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If Peter D is talking about NG, I think they are one of those POCOs. I know for example Eversource (the other major utility in New England) abhors anything other than 120/208Y and 277/480Y while their southern neighbor United Illuminating will actually offer 120/240 open delta for new construction no questions asked. When you drive through UI territory literally half the 3 phase services are open delta; usually the classic 50kva lighting pot and the smaller 25 or 15 kva kicker pot. NG and ES on the other hand its rare as hens teeth.

mivey said:
My preference, if I had a desire to get rid of them, would be to phase them out by not offering them to new customers. I really don't see why allowing them for existing is a big deal. I can get pretty much any standard transformer I need in short order and units for delta banks are pretty standard.
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It could be a big deal if they upgrade from 4.16kv to 13.8kv. I mean its physically possible, but from an operational standpoint:


1. The risk of ferroresonance that did not exist prior.

2. Having to order a none standard pole pig (for NG anyways) (none CSP, double bushing, possibly 13.8kv instead of 7.5 kv)

3. Having an none standard odd ball to worry about during a fault or emergency storm restoration.


#1 can be mitigated by an open wye delta bank (what ES usually does when the must keep a secondary delta), but considering 3 167kva pigs are in place NG would have to purchase 2 500kva pigs to obtain the same capacity. Plus, under heavy load an open delta does not perform the same way a closed bank would, in fact most pole pigs manufactures make note that T and open delta connections should be avoided where the load is predominately motor. Though I am willing to say that thinly as I've heard from others open delta banks are frequently used for irrigation pump shacks out in California without known issue.


Edit: I just want to add I don't disagree with you. I am sure the one step at a time is also at play, if not entirely, but at the same time the pump hut might be a question for NG.
 
mbrooke said:
If Peter D is talking about NG, I think they are one of those POCOs. I know for example Eversource (the other major utility in New England) abhors anything other than 120/208Y and 277/480Y while their southern neighbor United Illuminating will actually offer 120/240 open delta for new construction no questions asked. When you drive through UI territory literally half the 3 phase services are open delta; usually the classic 50kva lighting pot and the smaller 25 or 15 kva kicker pot. NG and ES on the other hand its rare as hens teeth.
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I'm not a huge fan of open delta. It serves a function but I would consider it a last option. Closed delta is fine with me if it is fine with the customer.


mbrooke said:
1. The risk of ferroresonance that did not exist prior.
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Low risk at that voltage.

mbrooke said:
2. Having to order a none standard pole pig (for NG anyways) (none CSP, double bushing, possibly 13.8kv instead of 7.5 kv)
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It's just a transformer. Readily available and easily obtained from manufacturer. These are not special order items for the manufacturers and most have them sitting in the yard. If you don't want to wait a day or so, keep a few spares in your yard. Not a deal-killer.

mbrooke said:
3. Having an non standard odd ball to worry about during a fault or emergency storm restoration.
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If you allow these on the system, there should be spares in the yard. If it is the only one left on the system, then keep a dedicated spare. Suppliers can usually get one overnight from the manufacturer or another utility if you get in a bind.

If the utility goal is to get rid of them, then get rid of them.

mbrooke said:
#1 can be mitigated by an open wye delta bank (what ES usually does when the must keep a secondary delta), but considering 3 167kva pigs are in place NG would have to purchase 2 500kva pigs to obtain the same capacity.
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Bigger than that would be needed for large motor loads. I'm not an open delta fan and would rarely recommend one on a three-phase line. However, open delta serves a lot of remote three-phase loads (economics being the factor).

mbrooke said:
Plus, under heavy load an open delta does not perform the same way a closed bank would, in fact most pole pigs manufactures make note that T and open delta connections should be avoided where the load is predominately motor. Though I am willing to say that thinly as I've heard from others open delta banks are frequently used for irrigation pump shacks out in California without known issue.
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Properly sized they work OK. I "oversize" to help with voltage regulation.

mbrooke said:
I just want to add I don't disagree with you. I am sure the one step at a time is also at play, if not entirely, but at the same time the pump hut might be a question for NG.
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Of course only NG knows for sure. We are just playing speculation. Hey, it beats ditch-digging.:)
 
mivey said:
Low risk at that voltage.
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But still possible, with the risk elevated with anamorphous cores.

It's just a transformer. Readily available and easily obtained from manufacturer. These are not special order items for the manufacturers and most have them sitting in the yard. If you don't want to wait a day or so, keep a few spares in your yard. Not a deal-killer.

If you allow these on the system, there should be spares in the yard. If it is the only one left on the system, then keep a dedicated spare. Suppliers can usually get one overnight from the manufacturer or another utility if you get in a bind.
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IF you allow them. POCOs that don't often like to have the yard streamlined.



If the utility goal is to get rid of them, then get rid of them.

Bigger than that would be needed for large motor loads. I'm not an open delta fan and would rarely recommend one on a three-phase line. However, open delta serves a lot of remote three-phase loads (economics being the factor).

Properly sized they work OK. I "oversize" to help with voltage regulation.
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Which furthers my theory. Going over 2 500kva pigs pushes padmount.


Of course only NG knows for sure. We are just playing speculation. Hey, it beats ditch-digging.:)
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It does :lol: :)


Peter D, can you ask NG about that pump station, or at least what they do with an existing open delta service?
 
mivey said:
My preference, if I had a desire to get rid of them, would be to phase them out by not offering them to new customers. I really don't see why allowing them for existing is a big deal. I can get pretty much any standard transformer I need in short order and units for delta banks are pretty standard.
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NG does not offer them anymore as a new service, you get wye or you get nothing. ;) Now, you can get primary voltage delivered and do whatever you want with it after that, but all but the largest industrial customers don't have that luxury.

The only delta services that still exist are to mills and the odd machine shop or industrial building that had their service installed many decades ago. These installations are few and far between now as the mills are being demolished or converted into apartments.
 
mbrooke said:
Peter D, can you ask NG about that pump station, or at least what they do with an existing open delta service?
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I don't know anyone to ask, but I know they will remove an open delta service the instant they have the opportunity. As I said before, this will happen when the service needs to be changed or upgraded.

This whole thing seemed interesting to me because I know their tendency to remove anything old and odd ball whenever the opportunity arises. If I can say one thing about NG, it's that they like uniformity and simplicity in their construction standards and practices.
 
peter d said:
I don't know anyone to ask, but I know they will remove an open delta service the instant they have the opportunity. As I said before, this will happen when the service needs to be changed or upgraded.
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So they basically force customers to upgrade?



This whole thing seemed interesting to me because I know their tendency to remove anything old and odd ball whenever the opportunity arises. If I can say one thing about NG, it's that they like uniformity and simplicity in their construction standards and practices.
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Oh yes! :happyyes:
 
peter d said:
The only delta services that still exist are to mills and the odd machine shop or industrial building that had their service installed many decades ago. These installations are few and far between now as the mills are being demolished or converted into apartments.
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We have one in providence on the docket. It's ungrounded 600v delta. A few years ago, ng took out the transformers which were sitting behind a fence in a recess of the building, and refed it with regular pots (but still 600). It was wild, those things were big!
 
electrofelon said:
We have one in providence on the docket. It's ungrounded 600v delta. A few years ago, ng took out the transformers which were sitting behind a fence in a recess of the building, and refed it with regular pots (but still 600). It was wild, those things were big!
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Around this size?


3_Transformer.jpg
 
electrofelon said:
The original ones on the ground in the vestibule stood around 6 feet high. The new ones on the pole are pretty small, probably not bigger than 25's - not much demand in that building for years.
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Probably 50s. Most POCOs go pad over 50, but you do get that occasional 167 or 500 thats pole mount :eek: Of course there gets to be a point where a 2 pole platform is better since a lot of existing poles supporting anything over a 150kva bank turns into a leaner, even with proper guying. Of course thats not to say platforms don't get abused either. Have you ever seen 3, 3000 KVA pigs get poled? :D:eek::lol::thumbsup:


http://www.ipernity.com/doc/connecticut_power_lines/16724589


Complimentary regulator to boot:

http://www.ipernity.com/doc/connecticut_power_lines/16724337


Overall setup compared to some mini vans to give you the idea of their size:

http://www.ipernity.com/doc/connecticut_power_lines/16724319
 
nice pics. There is a two pole platform down the road with pretty big units on it, Ill take a picture of it next time I go by. I know I have seen some absurd singles around but cant recall any specifics or their location. You have me on the lookout now.
 
electrofelon said:
nice pics. There is a two pole platform down the road with pretty big units on it, Ill take a picture of it next time I go by. I know I have seen some absurd singles around but cant recall any specifics or their location. You have me on the lookout now.
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LOL! :) Id certainly be interested.
 
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