Tap Changers

[Special ED]

Power company here the voltage is pretty reliable.. No big fluctuations like in the winter months of some places that would require changing the tap settings..

Swamp out of curiousity why would you change the taps to get more life out of the pot? The taps add or reduce the windings on the primary coil to allow adjustment for the voltages needed.. For example your primary fluctuates more than 5% up or down or more would be the only reason for changing them. Almost all times theres a fluctuation like that around here it is a power quality issue such as caps, or regulators on the line or in need of repair.

I could see during a peak load time in the hot summer months or the ice cold months a need to change taps but it is un-realistic to change every tap in the city for a short time and go back to change them..

Thats I've been taught and practiced cause they are pretty obsolete around here when it comes to their usage.. Anymore insight would be awesome cause if theres something I dont know bout increasing the transformers life I'd like to know.. Transformers are getting pricey and my customers a getting tougher to convince into buying them.

[Pootnaigle]

Tap changers are purdy cool. The ones that affect us the most are built in to the substation transformers and adjust themselves automatically as the load rises and falls. The taps on distribution transformers can be helpful but as you said generally hafta be reset at a later date. This aint the case if the substation transformer dont have taps. In those cases the taps can purdy much be set on the dist tubs and left forever.They are also handy when maybe using 13.8 pots on a 13.2 system or vice versa. I spoze they are just a handy tool to help us get through problem periods without sacrificing customer service. Me I like em.

[Special ED]

Sounds like a cheap fix to a power quality issue.. But I can see where they are very helpful when needed..

[lewy]

We do not have them on any of our transformers for 16 kv, but we do have them on our lower voltages, but rarely use them. Where they do come in handy for us is we use 1 transformer for both our 12kv & 13 kv we just lower the tap completely when used on the lower voltage.

[wtdoor67]

Used to raise the voltage some on the end of rural lines on 7200 and below.

Used 14.4/24.9 pot hooked delta in 13.2 wye lines. Oil field. The 13.2 was pushed up to about 13.8. Had to raise the tap on those pots one position.

[Special ED]

Ya missed what I said Ed. That was back in 70-71....little rural muni. Yeah, "Cheap" was a word they used alot.:D

Nah I didnt miss what ya said Swamp.. lol Gotta love the Munis tryin to save a buck only to spend a 100 of em..

[Trbl639]

Used to raise the voltage some on the end of rural lines on 7200 and below.

Used 14.4/24.9 pot hooked delta in 13.2 wye lines. Oil field. The 13.2 was pushed up to about 13.8. Had to raise the tap on those pots one position.

Same here........

Some have 5 position 2.5% tap changers.where each step raises/lowers the voltage 2.5%.......... others have 3 position 5% where each step will raise or lower the voltage 5%....center tap being 100%

[BigClive]

Nah I didnt miss what ya said Swamp.. lol Gotta love the Munis tryin to save a buck only to spend a 100 of em..

In the case that Swampy described they'd be saving a lot. It sounds like the distribution was loaded to the point that there was enough voltage drop to justify tapping the transformers up to compensate. The other option would be to replace EVERY transformer and insulator on the line and step up to a higher primary voltage.

Hence why it got extra life out of the transformers I guess.

[climbsomemore]

I have had to dial a few in ... usually in spots that were either very close to the sub...or at the far end. Now and then the load study would find a customer with a load and voltage issue within what the tap changer could handle too.

On delta circuits we would dial em up or down too. Delta is very hard to get good regulation on and the tap changers (inside the tank, porcelien knob on the old side bushing transformers) usually offered enough correction.

[climbsomemore]

but these days I get to point and whistle a little bit more that I did 30 years ago.

Swamp...you do know that after 25 years or so--- some of us get paid for what we know in addition to what we can do.

[wtdoor67]

I remember changing some that you had to take the lid off and physically unbolt the leads and move them around. You don't suppose they were PCB do ya? Maybe I could conjure up a law suit or somethng. Also, yeah, those you had to take the lid off and twist the dial. Actually the more I think about it I think we used them quite a bit. Never did on the 34.5 though, plenty of voltage there.


I tell you what. Gregg surely enough time has passed. You can reveal your past. We all have figured out you were with the CIA in Saudi. It's all passe now buddy. Give us some of those bone chilling stories when you were up a pole looking through those night vision goggles and calling in coordinates to a secret operative.

I gotta admit though it was a pretty cool cover, that Lineman facade. Bet old Hakim never even suspected. Lineman by day, secret agent man by night. Think they'll make a movie about it?

[wtdoor67]

They got so **** twisted up over those PCB's. I remember in the 80's when they thought if you touched it you would come down with cancer.

For a very short time PP&L made you wear a cheap plastic suit. I remember changing out what they figured was a PCB capacitor. Put on the plastic suit, climb the pole, send down the capacitor into a barrel. Unclimb the pole, take off the plastic suit and the little surgical mask and put all carefully into the barrel. Then close the locking lid on the barrel and take it to the warehouse to be supposedly be shipped to some disposal place.

Eventually they figured out the **** stuff was toxic only when burned. At least that's what I was told.

Had a dumb manager with PSO. They had a PCB spill from an old pole mounted transformer or something. They had a clean up crew out there digging up the dirt and bagging it etc. The lady who owned the property had some horses in the pasture and was concerned and curious. She showed up. The manager, who incidently is no longer a manager, remarked to her. That stuff contains PCB, you know which causes cancer. This lady's husband had expired of cancer a few months prior. How long before he was demoted? Not long.

[Pootnaigle]

Yanno when yer lookin at the youngsters doin it today yer really lookin at the future of linework as we know or knew it. I kinda have a different approach I tellem this is what we hafta do and I can stand right here n tell ya every move to make or you can use yer sperience and training n get er done. If I hafta stand there n tell ya everthin that purdy much means I dont think you know anythin. I jus tellem if ya run up on a snag Holler at me n I'll try n unsnag ya. Do I ever see em doin everthin the hard way??? yeppers I do n when its all ver I will ask em ummmmmm why dint ya do this.............. The good uns lurn and the bad uns aint gonna anyways

[Pootnaigle]

I jus membered a tap changin prollem I had once n it plum befuddled me. We took down a 3 pot bank 50s I bleve hooked up delta wye( that would be 2400/120/208 and I checked the voltage fore we kilt her out It was off the chart. Anyways I needed 1 of those pots on a 4160 wye n sure nuff each pot had a tap where ya hadda remove the lid and move the tap switch . So I made an educated guess and set the taps where I thunk they needed to be hung the pot and got absolutely nuffin outta it. Scratched my headbone alla primary was hot n werkin come to find out the tap switch had dirty contacts and moving it one position fixed the prollem.

[Special ED]

I was taught, when and if, ya ever had to change the taps, either on the inside or outside of a pot, ya should always flip the changer a few times, both left and right, and then put it back where ya wanted it.

I was too swamp.. I asked why and got the old "Cause I said so." or "Thats just how its done.".. Guess this answers my question. lol Makes alot of sense though.

[busman]

Question from an Electrician. Changed out a service the other day. Voltages (no load) were 124V and 134V on a 120/240V service. Is this a common problem. Is it even a problem? If it were a tap problem, I thought the voltage would be high or low on both legs symmetrically. Should I let the PoCo know about this.

Thanks,

Mark

[rcdallas]

Question from an Electrician. Changed out a service the other day. Voltages (no load) were 124V and 134V on a 120/240V service. Is this a common problem. Is it even a problem? If it were a tap problem, I thought the voltage would be high or low on both legs symmetrically. Should I let the PoCo know about this.

Thanks,

Mark

So what's your voltage like with a load on it?

Does it drop to like 70 volts on one leg and 180 volts on the other?

I'd check out the neutral...may just be on the utility side.

[busman]

So what's your voltage like with a load on it?

Does it drop to like 70 volts on one leg and 180 volts on the other?

I'd check out the neutral...may just be on the utility side.

It was similar with a load on it (a few volts lower on each leg). I posted the no-load voltages, because this might indicate that it's not the neutral. If it helps, I measured these voltages on three different days and they were very steady?

Thanks for any help.

Mark

[Special ED]

It was similar with a load on it (a few volts lower on each leg). I posted the no-load voltages, because this might indicate that it's not the neutral. If it helps, I measured these voltages on three different days and they were very steady?

Thanks for any help.

Mark

Sounds like they PoCo is givin ya too much juice! Which one you with? Ill let em know to adjust your bill accordingliy.

Plus or minus 10% i think it is, is ok.. Check your voltage drops and shifts. They will show neautral problems and or unbalances in the system...

[johnbellamy]

+ 0r - 5% is an acceptable range, on a 120v that would be 114v or 126v, ya need to check voltage at the transformer, it is probably a neutral problem, but when you say it is consistant, what is your reference, it is a wye primary or delta? At your source, you should not see a imbalance on your secondary legs. Put a Beast on it, it will tell you your answer.

A side story, one for Danny, or anybody jump on in. Had a lineman on standy by have a blown fuse on a wye/delta 120/240/208 closed bank, 7200/12470, took voltage at the customers panel, had odd voltages, so he called for crew, thought he had a bad pot, crew shows up changes the pot out, energizes it, same issue at the panel. What are your conclusions?

[busman]

All,

Thanks for the replies. I'm an electrician and I encountered these voltages in the course of upgrading a service. I had considered a bad neutral, but thought that unlikely since the total voltage is 124v + 134v = 258v. I would have expected the total voltage to be less than 250v under normal conditions. That's why I posted the question here.

The only additional info I can provide is:

Location: Northern Virginia (near Alexandria) - Dominion Virginia Power

Most of the local distribution is above ground, but this small subdivision (about 20 homes on a cul-de-sac) are on underground distribution.

The house in question is the first home in on the cul-de-sac. That is to say - closest to where the conductors come down the pole and go underground. I did some poking around, but without going in the neighbors yards, I did not locate the padmount.

This customer has not noted any ill effects from the odd voltages. I just hate to call out the PoCo if this is not an issue.

Thanks for any ideas.

Mark

[Lineman North Florida]

+ 0r - 5% is an acceptable range, on a 120v that would be 114v or 126v, ya need to check voltage at the transformer, it is probably a neutral problem, but when you say it is consistant, what is your reference, it is a wye primary or delta? At your source, you should not see a imbalance on your secondary legs. Put a Beast on it, it will tell you your answer.

A side story, one for Danny, or anybody jump on in. Had a lineman on standy by have a blown fuse on a wye/delta 120/240/208 closed bank, 7200/12470, took voltage at the customers panel, had odd voltages, so he called for crew, thought he had a bad pot, crew shows up changes the pot out, energizes it, same issue at the panel. What are your conclusions?We to have always been taught 5% +or- on your other stumper could be a phase out on lateral, I have seen 4x fuses at transformer banks blow and take out 65k at the take off pole causing crazy voltage on bank, might not be the scenario your looking for though.

[wtdoor67]

A side story, one for Danny, or anybody jump on in. Had a lineman on standy by have a blown fuse on a wye/delta 120/240/208 closed bank, 7200/12470, took voltage at the customers panel, had odd voltages, so he called for crew, thought he had a bad pot, crew shows up changes the pot out, energizes it, same issue at the panel. What are your conclusions?
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Take the bank apart and test each pot in a separate single phase mode. That'll tell you something. Perhaps one primary phase is goofed up. I have heard on overhead of one phase on the take off breaking off and falling over on one of the other and causing 2 of the source primaries to be the same.

Also capacitors might be unbalanced. Any other locations have problems?

[johnbellamy]

For your responses, like ya say Danny, it is actually simple, there was was nothing wrong with either one of the pots, I said took voltage at the customers panel, Not at the bank itself at the source, Just had a no neutral, kinda went with the other and a point of always trying to start at your source if ya can, work your way from there. Sorry I know I did not give alot of details, and the crew just did what they were called to do, but he was checking where it was easy access, and he could check the three phase secondary voltage, his goofy readings were phase to dirt, but he did not tell anybody that. So the customer only had the three hot legs going to that panel, where he ran his pump, so phase to phase was good, but phase to dirt was the odd voltages, not phase to system neut at that point.

Nobody that showed up checked the guys work, tested any trans, or even checked voltage at the bank when finished. All the basic steps to do. You can get caught pretty easy on things, and you should always check things out for yourselves when you arrive, just not take a guys word for it.

[Special ED]

Got to blow an engineers mind here in Louisville. Got a call the other day narrow backs said a transformer blew up and needed me to come in and change it out. Even though im laid off I was a good sport and went in cause I could use the money and its usually good for a laugh when a narrowback trouble shoots then call me for help.

Anyways I go in and supervisor advised narrowback not to touch anything since hes not qualified nor does he have the equipment. Well I get on the scene and set about trouble shooting the transformer in question. Narrowback informs me hes found the problem and is in the middle of disconnecting 1000 KVA padmount to move in to the spot of the 2000 kva pad mount that is blown up. I said go put whatever you've taken apart back together and then go sit in the truck till Im done.

13.2 Delta going through a gear feeding a 2000 kva transformer with no power to the panels inside.. Check the gear since its got all the fancy monitors and stuff. Its sayin bout 14.5 kv phase to phase all around so primary to that point is good. Load side indicators indicating its hot. So I check the can. Get less than 1000 volts on all phase to phase readings through the bushings on the can and the narrow back is sittin there and says "Told ya its bad! Its hot on the primary and but its not on the bushings so Its not going through the transformer like its supposed to." By this time I was pissed so I mouthed off bout him being a dumbass and has no clue what hes doing out there and then inform him the primary is in fact not hot. Well only the 2 outside phases are out and the center one is in..

He didnt believe me cause the "load side indicators were lit" showing its hot. That would have been true if the load side indcators were installed on the load side of the fuses but they werent. Opened the gear and looky there! A and C phases are blown.. Sometimes I amaze myself with my common sense..

Anyways yank the bayonets and try the primary it holds like I knew it would. Disconnect the service legs and plug the bayonets got my 512 to 515 phase to phase all around on the 480 service.. So I know the can is good.

While disconnecting the service seen couple of the X2 connections were hot and had melted insulation.. Disconnected them all from the can and the bus duct and megged em out.. TA DA!! out of the 3 runs of 750 one is bad burnt all three phases plumb in two. Narrowback swears its impossible since he installed the wire not 2 years ago. I handed him my meggar and said prove me wrong.

Long story short replaced the run of 750 and got the power back on..
Thats when the engineer mentioned the power being too high and playing hell with some of their sensitive equipment. I was like yeah its comming in bout 14.5 Delta instead of 13.2 delta and your getting bout 510 delta on your 480 service here.. Engineer asked if I could fix it or if I knew what to do bout it.. "Sure I say." Narrowbacks callin the shop thinkin Im gonna mess with the power company equipment cause if i was caught and not doing offical work for them I'd be fined. Well i dump the feed to the 2000 KVA can turn the tap changer from the 13.2 setting (C) to the 13.560 setting (A) and go back to energize. Would ya look at that! 490 phase to phase all the way around!

Blew that engineers mind and ole sparky the narrowback was wanting to know how I changed the voltage so fast and since hes a real religious type of guy I told em "Me an Jesus got an understanding on who controls the power round these parts and I made him reduce it for me." and just left em standin there dumbfounded.

[electric squirrel]

You went out on a trouble call even though your laid off????? How the hell does that work??? I think there is a faint smell of cheese in the air......

[wtdoor67]

Swimpy, he say dey don't use dem tap changers anymore. He so smart.

Try a piece of hard drawn #6 on your belt. Handy to hang nuts and washers. Ha, ha, ha.

[Special ED]

You went out on a trouble call even though your laid off????? How the hell does that work??? I think there is a faint smell of cheese in the air......

Getting unemployment for the shortage of work. Its like being laid off but not really.. It does mess up my unemployment when I get called out and it really screws me.. Im in the works of headin down the road somewhere else but for now Im sittin at home unless theres an "emergency" call.

[Special ED]

Swimpy, he say dey don't use dem tap changers anymore. He so smart.

Try a piece of hard drawn #6 on your belt. Handy to hang nuts and washers. Ha, ha, ha.

I find the 6 hard drawn on your belt works great for catching service drops and open wire secondarys while climbing.