Delta vs Wye

[lewy]

I am just curious is there still a lot of new delta primary & to a lesser degree secondary still being built in the states?
I realize it would be expensive to convert it all to wye, but is that a long term plan or is the delta actually preferred?
We try & convert a lot of our lower voltages up, but it is a slow process.
Up here delta is extremely rare & new customers can only have wye secondary.
From some one who has only worked on wye primary & very little delta secondary I would think a wye system is a lot easier to work on for example we are not aloud to rubber glove 27.6 kv delta in this province, but we can 27.6 wye.

[topgroove]

A wye Primary is certainly easier to deal with. For lineman outside of the NorthEast many will never deal with a delta in their career. Backfeed and the ability for delta to take a grounded phase is something a lot of lineman can't wrap their head around. I've worked with Delta and wye my whole career.

[wtdoor67]

The only restrictions I ever encountered with gloving was governed by the phase to phase voltage and had no bearing if it was Wye or Delta.

In some area of the US delta is quite common. In small static (no growth) communities it is just not cost effective to convert to Wye usually.

The most common probably is 4160 Wye and 2400 Delta being in the same area. Same pots, just different hookups. Also have seen 7200 Delta and 12470 Wye in the same area and using the same pots.

As far as I know LAWP still uses a majority of Delta for their distribution and also that area where Topgroove works.

There used to be some LAWP guys who posted on here and we had a discussion once. They claimed the Engineers asserted that a Wye system wouldn't work well in the Los Angeles area because of the grounding problems.

As far as Delta secondary. Yeah lots of it in the US for the most part. However I'm sure some would dispute that. A guy I worked with had worked in DC and claimed that Delta secondary there was scarce as hen's teeth.

As far as I know the REC's in the US were all Wye from the git go. They were created in the 30's and I think started mostly with 12470 and now most seem to be 24.9KV. Probably makes the logistics easier.

[Trbl639]

There's not much Delta primary left in this neck of the woods, except a few plants that maintain their own...........it's just about all wye....7620/13.2, and 19.9/34.5......some of the co-ops/munis still using 7200/12470 and 14.4...........

As far as secondary, it's mixed probably about 50/50, delta and wye, although most of the newer businesses, small commercial and industrial are going to wye........

Like Top said, most lineman these days are not real keen on Delta Primary..........cause all they have worked is wye........got what little experience I have with Delta Primary came from my military time, throwing that ground in there, sure messes with peoples minds......

[wtdoor67]

In conjunction with some other work we were doing once I noticed it would be real simple to cut over a small portion of 2400 Delta to 12470 Wye. I suggested it to the foreman. He thought it a good idea and asked the Supt. about it that evening. Everyone thought it a no brainer.

The next day or two we did it. Try as I might I could not talk the foreman into grounding one phase of the Delta as it would have facilitated the job. We did not although I urged him to and said it was a routine thing. He hadn't messed with much Delta and we didn't ground it. He was leery.

I've often tried to explain it thusly. "Look, ever time you build a Wye/Delta bank and midpoint ground the lighting pot. You're putting a ground on a Delta. Yes, it's a lower voltage etc., but still a Delta."

Once I hooked a mechanical to the secondary neutral and asked an old ground hand. Jake what do you think will happen when I put this on this phase? He replied. You'll start the biggest fire you've ever seen. I slapped it on the phase and screwed it down. He'd never seen a delta primary grounded before. He'd worked plenty for a small muni with delta but just didn't know much about it.

And yes, I know. You better make sure another phase isn't already grounded before you do this.

Jake asserted that you couldn't phase a 2 pot bank with a 3 pot bank. We made a bet. $5 dollars I think. We were contractors and I asked the old power co. foreman if this were so. He sorta glared over his cigar and said. Why hell yes. I took Jake's money.

[Trbl639]

Shortly after I hired on with the power company, we had a new kid, been working 8-10 years for another company hire on, and we were building some 2 of 3 phase into some irrigation wells with open/delta 120/240 banks..we also built the meter loop for the customer, using an HQ5 meter can (5 terminal/center lug on the bottom had a ground bar and a drop down bar in between center-top and center-bottom lug) anyway, we always grounded one leg of these services, at the bank and at the weatherhead.........got this bank built and was time to heat it up, and the new kid was told to close the bank in..........

He said, ain't no way....that damn thing is grounded and you're gonna blow a fuse....explained the delta and the grounds, and he was leary, but closed it in..........

He had never worked around delta at all, except secondary, had never built an open/delta bank, and didn't understand it!!!!

Reason we grounded the center lug, was the farmers/electricians had figured out they could get un-metered voltage off that hook up, even without a meter plugged in, if the bank was still hot............and the serviceman had failed to open the 'center-lug' when he pulled the meter.........with the ground, it didn't happen!