Interesting

[dbrown20]

situation occurred at my former workplace. While I was there a contractor cutover from 4160 to 13.200 in a small town. They seemed to take quite a long time as I recall, although they were called off on a storm once I believe. Anyway they finally completed the job. Well they did miss a portion that was single phase and had a step down pot that served about a dozen pots. Any way they finally left town and everything was hunkydory for awhile. About the time I retired our men were doing that single phase step down portion. Recently a former co-worker called me and laughingly related what happened after I was gone. The poor contractor had constructed about a dozen closed Wye/Delta banks and had grounded down the "floater". Some banks even had single bushing pots in them. Anyway to start everything an 85 K lateral fuse had blown. The troubleman arrived to find multiple banks blowning fuses and before the night was over they had to change about 6 transformers and went in early one morning and rewired about 5 banks. Anyway when the fuse blew this caused the grounded down banks to begin backfeeding the blown phase. This caused overloads on some of the pots feeding from this phase I guess. I didn't really get all the details but it was quite a problem. I've known this was a bad way to hook up a bank, and had seen a few minor problems before from this mistake but nothing to this extent. This was a roughly $20,000 mistake I was told. This same poor contractor burned up 3 regulators by not connecting them to the system neutral when I was there. This supposedly was a 6 figure mistake. They're gonna have to start training those people. dbrown20

[Trampbag]

Many utilities have a standards book and the job prints refer to the page or pages for each structure including the transformer hook up showing diagrams of the high and low side connections and if paralleled or series. This saves a lot of headaches and problems. SDG&E had one of the best information packages I ever used except it was difficult to read all the info on the prints. It was a lot for a new foreman to take in but once you got your head wrapped around their information it was hard to make a mistake especially like what you are talking about.

Almost all the larger utilities have Standards books available or include standards prints pertaining to the job in the job package. Smaller utilities may not have the resources to include that kind of information. Any construction foreman working on a project without all the info had better be boned right up on his electrical knowledge and be on the ball. A tall order to be sure.

One place I worked for a utility they contracted out a 10 or 12 structure line with several single phase transformers to be installed. The line was an extension of an existing line but the twist was that it was 2,300 volt Delta fed from a 7.2/12kV and a step down transformer bank. It was the only Delta primary in the whole area.

It was certainly the only Delta primary the construction crew had ever seen.

When we went in to energising the new line and checking the transformers for voltage we got zip, nothing. Upon closer scrutiny it seems there were 4 wires on the new primary. Apparently the construction crew didn’t find a system neutral on the existing 2,300 and went back to the step down bank and installed a system neutral and hooked all the new transformers up Wye.

We later looked on the print and not once did it show any diagrams of the desired construction standard because there was no Delta standard, because that was the only Delta primary in the entire utility, 30 some poles and 8 or 10 transformers. It was embarrassing for everyone involved including the engineer and planners.

[dbrown20]

had standard books available. Probably just didn't know how to read them. In my experience standard hookups are known from early on in a Journeyman's experience. The spacing may not be known but the hookup itself is never forgotten.

We had a contract crew working once on the property of a utility where I once worked. One of their assignments was to build a "208" bank. Now this was a loosely supervised operation as I don't remember that the co. even had an inspector to check up on these people.

Anyway Sam's crew built the bank. The serviceman went by later to run an underground service. He came to the shop eventually and related that someone would have to go and redo the transformer bank. We went by there and Sam had built a 3 pot bank that consisted of 2 CSP pots that he had gotten off of a wreckout, and one conventional pot. Also instead of building a Wye/Wye hookup he had constructed a Wye/Delta. To give him the benefit of the doubt, later someone approached him and said. You know that was supposed to be a 208 bank up there Sam. He growled. They got 208. We supposed he was referring to the wild leg. Anyway we went up and took everything down and made a Wye/Wye 208 out of it.

I got tickled later. This same crew was tasked to build a 2 pot bank that was on the 4160, but about 3 or 4 spans away from the system neutral. We had the right pots for a non-neutral system, but he took out some 2400/4160 pots and tried to make them work. After he reported no sucess we went by and took a look. From the amount of empty fuse boxes on the ground it seems as if they had hooked it every way possible I guess. Anyway instead of changing the pots we just strung in a few spans of neutral.

Worked for a municipal once. They had a crew once build a wye/wye 208 bank once. Instead of hooking the high side neutral into the system neutral, they "floated" it. This caused the bank to burn up some of the customer's single phase stuff. After the smoke settled the old superintendent, who didn't know much more than the hands, said. From now on just ground every bank to the system neutral. They had multiple banks of closed Wye/Delta all over town with the floater hooked into the system neutral. I went on one change out once where the trouble people had diagnosed a bad pot in a 3 pot bank. It was grounded to the system neutral and so I thoughtfully "floated" it. Well after changing the bad pot the voltage was still screwed up and so with further checking I found another pot bad. It had of course been operating as a 2 pot bank for awhile until another pot went bad. Later while driving an alley one day I noticed a 3 pot platform bank with the high side hooked into the system neutral. Hold on. I said. I'll just go up and float that booger. Well I did and quickly a clerk came out of the drive up bank and said. Something just went wrong with our power. None of the teller machines work etc. I immediately went back up and grounded the floater and deciphered which pot was bad. We changed the bad pot and truly "floated" the high side. Leaving I noticed another platform bank with the same situation. Piss on it. I said. I'm not messing with anymore of those friggin banks around here. dbrown20

[PA BEN]

The first morning at the Motel in the town of my interview for my new job, I walked out and as a linemen I saw an open cutout on a power pot of a three pot bank across the street. I said to myself that there single phasing, but wait those are single pushing transformers. Why would anyone build a Y delta close bank with those transformers?

At my interview I brought this up and was told, that was the way they built them in the day. This utility use’s a lot of single bushing transformers so they used them. We don’t build them that way any more. But there are a lot of them out there. Well two years later we had a truck pull down a 3 phase line down town, it must of blown at least one sometimes two fuse’s in each bank on that feeder down town. The wind storm we had last December did the same thing. At least they didn’t say, “that’s the way we’ve always done it.” :cool: