for aep!

[44kv]

for all you aep guys out there i have a question? ya'll have a bank on the system that is 277/480. I heard that you have to close a cut out door on it before you de-energize and open the door before you re-energize it.( or the other why around not sure?) what kind of bank is this, what is it for, (the opening and closeing the door before and after i mean). what is this bank use on most of the time? and how is it wired? is it a delta, or wye?

[dbrown20]

You need to study your transformer book some. A 277/480 bank is simply a Wye on the secondary side. Very common. The 480 three phase is used like the 480 delta. For industrial and any load that requires 480 three phase. The 277 portion is sometimes use in some lighting instances.

The opening and closing procedures you mention are associated with some Wye/Delta hookups of approx. 20 KV and above. This is to prevent ferroresonance and consists of an extra grounding cutout that is closed before the other 3 cutouts are closed and then opened after they are closed. Of course the reverse procedure is used when opening the bank up.

Most companies are beginning to prefer the 277/480 hookup. Easier to regulate in some instances I believe. dbrown20 Hi Bill.

[electric squirrel]

Mr. Db , so what you are say'n is you use a 4th cut out? What exactly are you ground'n ? Please elaborate a little more, out here in Cali we use kyle switchs if we have a ferro problem, I am an ape (just a few more monthes left) and I havent yet worked on a wye system , does this 4 cutout set up work on a delta system too? I thought that the reason for switches was because you need to close in all phases at the same exact time, not possible with sticks, so you use a gang operated device.Enlighten me a little more please, like I said I havent seen this situation yet and want to know all I can learn....E.S. :confused:

[dbrown20]

On a Wye/Delta hookup there is some possibility of ferroresonance when the high side is "floated". This of course would be on a 3 pot bank. Ferroresonance is more likely to show up at about the 20 KV primaries and above. I've seen it on 34.5KV. When the cutouts are closed one at a time is when your problem may occur. The ideal situation is without load, and smaller transformers. I have seen a piece of #6 with 2 hot clamps used with a shotgun and going from the neutral or a ground to the "floater". After all 3 cutouts are closed then the #6 is removed. To make it handier some companies have just installed a 4th cutout. The top of it is hooked to the floater and the bottom to ground. Then you just close the ground cutout and then close the 3 fused cutouts. Then open the ground cutout. Reverse procedure when opening the bank. I've seen quite a few setups like this on REC 24.9/14.4 KV. 10.4?

No, this doesn't happen on a Delta primary. dbrown20. Hi Bill.

[Trampbag]

In California mostly Delta primary feed is used. I think DBrown20 is referring to a Wye primary connection. Correct me if I’m wrong.

There are many ways to skin the same cat, and different utilities and private plants have slight differences for connections, some I still haven’t understood the reasons why.

[edski104]

its just for the porpose of energizing the bank that you close the 4th cutout,which is in the neutral,to keep all the pots grounded. after the bank is energized,you can open up the neutral of the primary and let 'er be. this is so if one can goes out,the other 2 cans will not pick up the load of the bad can and you won't know that you have a bad pot,which will happen if all 3 cans are tied together on the primary neutral and grounded. and so you wont blow any of the la's which does happen from time to time. :cool:

[44kv]

now i get it. dbrown you said to look in my tx book, well i dont have one. I ask duke energy about the book when i was at a op center but they dont have them. they have a tx workshop that splits all there banks for them they dont really build banks. There txs only have two sec bushings on them for bank building. so if they need to build a 75 then they go two the yard and get 3 25s and the voltage has to be 208/120 then each tx has a hot secbushing and a neu. so any body could build the bank. checked on line the ge book is 185 dollars!!

[dbrown20]

Those little old GE distribution handbooks are only about 3 or 4 dollars. You don't want the super duper deluxe model. Just the little one. Most shops have them floating around. Keep your eye peeled and you might be able to appropriate one for your own use. Also get yourself a Kurtz Lineman and Cablemans Handbook. They can be bought used pretty cheap on Barnes and Noble.
277/480 pots are pretty simple. Only 277 turns on the secondary side and only 2 secondary bushings. I think it says 277/480 on the label but you actually have to have 2 at least to get 480. Saw a guy hook a bank delta on the secondary side once and he had a 277 volt 3 phase secondary. We had to change it to Wye to get 480. dbrown20 Hello Bill, anything subversive?

[electric squirrel]

44, private message me and I'll send you one of those x former books, I got two, I can spare one to help you out. E.S. :cool:

[dbrown20]

44, private message me and I'll send you one of those x former books, I got two, I can spare one to help you out. E.S. :cool:

Now that's what I call being brotherly. dbrown20

[electric squirrel]

44 got your message , put it in the mail asap! E.S. :cool:

[44kv]

sorry e.s been out of town! thank you very much the book means alot to me and agin thanks!!!