Primary wires from the Power Company

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james wuebker

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Location
Iowa
For years we had approx. 483 volts to this building. Just checked it the other day and found it to be between 453v to 460v. A lot of the machines here are not working correctly but still working. There's a lot of machines that have step down transformers to 24vdc which is now running low. Normally they would be running 28 vdc. Also all the other secondary transformers 120/208 & 120/240 are running lower. The power company told us they didn't put regulators in the primaries thru this area. They said that it's like this thru out this area and no one had a problem with it. I told them that it needs to be fixed correct. They said it could be up to an year before it's fixed. Told them to turn up the voltage to this area and they said they will look at this. Any ideas what I could say or do to get the proper 480v to this building? 4000 amp service now but only drawing around 2500 amps. What can I tell the power company to get them moving a little faster? Remember that everything in this building is tapped for 480v not 455v. Any ideas.
Jim
 
Re: Primary wires from the Power Company

as long as they are providing power to the service point that meets the specifications they have to meet, yoyu are not likely to get much of a response from them. It's not an urgent issue with them.

It is less than 10%. I don't see why your stuff is having so much trouble with it.
 
Re: Primary wires from the Power Company

I agree wiht Zog. Check the tap setting on your transformers. If its the utiltiy transformers they will have to adjust the settings.
 
Re: Primary wires from the Power Company

Bob, can't just hook the wires on another tap on their transformer. The power company didn't put regulators on their primary feed wires in this system here. They thought they didn't need them so now when people in this area (factory) uses a lot of power you will lose voltage. With it being hot here in Iowa A/C's are running. The power company forgot to figure that in. So now if they put the wires on a another tap and the A/C's aren't running we then will have 480v but then the taps will be wrong.
 
Re: Primary wires from the Power Company

Request the utility to change the transformer tap. Unless it is a very unusual transformer, it has taps for 95%, 97.5%, 100%, 102.5% and 105% rated primary voltage.

You are running about 5% below normal at 453V on the secondary (95% of 480V). Going to the next lower primary tap will boost secondary voltage 2.5%. If the system voltage does go back up to historical levels, you will have 483 +2.5% = 495 V. That is within normal equipment ratings and tolerance, especially when you consider voltage drop to the equipment.

My experience in operating large industrial facilities is that high voltage is always preferable to low voltages.

Changing taps should be a few minute project unless the transformers are older, oil-filled pole mount types with the taps under the lid in oil. On most transformers, tap changes must be done de-energized, so you need an outage.
 
Re: Primary wires from the Power Company

JAmes
If the transformers are utility owned they will have to make the change. Pole mounted transformers require that the utility remove the top and go inside of the transformer and make the change.
A pad mtd transformer taps can be changed by rotating a tap dial while the transformer is de-energized.
As RCW said you are about 5% low during the peak
load. During the off peak time of the year the voltage will rise but it probably won't be a problem. Where are you located?
 
Re: Primary wires from the Power Company

Bob, this is a 2500 kva transformer on a pad. The company is expanding and will also have another 2500 kva transformer added to the place. Will have 2-4000 amp mains there. I really want the problem correct the right way. They said that if they can get regulators on the primary wires that we should be at 480 v all the time even if it's peak power time. But again it could take up to a year. This company has a lot of injection molding machines and a ton of robots. The dc voltages supplying these machines from transformers within the machine has to be pretty close or could burn up input or output cards plus control valves. If voltages are to low they don't react fast or run at all. Hate to try to change every machine transformer to get these voltages then later the main is back to 480 volts. Just trying to think of want to stay to the power company to get them moving faster. Also if there's 100's of motors drawing more amps at this lower voltage would that make the meter spin faster. More money for the power company.
Thanks!
Jim
 
Re: Primary wires from the Power Company

I'm not clear on the problem.

Is the service voltage fluctuating more than what's guaranteed? Is it guaranteed?

Isn't there a definition of what parameters the service will meet?

:confused: :confused:
 
Re: Primary wires from the Power Company

Jim, most public service commissions require the electric utility to maintain the voltage to within about 5% of nominal. If the power is within the parameters that the public service commission will allow in your area, you are SOL. Your equipment should be able to handle 10% variation (we get 5% and you get 5%). If the voltage is outside of those limits, file a complaint with the public service commission. :D
 
Re: Primary wires from the Power Company

James, I think either you are not explaining the probmen so we can understand it ot you do not understand the purpose of transformer taps.

Schedue an outage, conduct a TTR test on the transformer and compare to nameplate data to verify you do not have any shorted windings, if the TTR test is good, change the tap to match the actual primary voltage, this should give you a 480V output to the plant. When the utillity fixes the voltage problem, reset the taps.

"The dc voltages supplying these machines from transformers within the machine has to be pretty close or could burn up input or output cards plus control valves. If voltages are to low they don't react fast or run at all. Hate to try to change every machine transformer to get these voltages"

I do not understand why you would need to change every transformer or how you are getting DC from a transformer.

"Also if there's 100's of motors drawing more amps at this lower voltage would that make the meter spin faster"

A KWH meter uses voltage and current inputs, your bill will stay the same.
 
Re: Primary wires from the Power Company

James, like Zog said, you only need to change the tap on the 2500 kVA pad mount transformer. That will boost the voltage on the transformer output and all voltages in the plant will go up.

You will need to schedule an outage with the utility, turn off power by opening your 4000 amp breaker and pulling the primary fuses or switches. Then adjust the tap changer on the transformer. On pad mounts it is usually behind the locked doors where the incoming power cables are. Check the nameplate data.

If the transformer belongs to the utility, they need to make the change.

One way to make sure you move the tap the correct direction is to measure the 480V at no load just before you kill the primary power, then measure again when you first energize (and before the power company guys leave). It should go up 2.5% for each tap.

Zog?s suggestion of doing a TTR test is a good one, but you could get by without it. You might want to schedule some maintenance on the service equipment as long as it has to be down anyway.

Good Luck,

Bob W.
 
Re: Primary wires from the Power Company

Ok guys, I do know about transformers. Got with the power company and they will change their taps on the transformer. The problem right now is the voltage goes down to 455v then might change to 484v. The voltage is now fluxuating. So if they change the taps now and the voltage on the primary side goes up won't it also change the secondary. So now they change their tap on the transformer to get our 480v and then the primary side voltage goes up, wouldn't we have more than 480v on our secondary side. Now on the dc voltages. The machines are plastic mold injection machines. The feed is 480v then there's a secondary transformer in the machine to step down to 240vac. Then for the output and input cards and other dc items there's a transformer to step down from 240vac to approx. 28vdc. There's taps on the transformers letting you tap at 220,230, & 240vac to get your 28vdc. All the machines have these. So lets say that your 480v is coming to the machine and the secondary transformer will give you 240vac. We have 28vdc. Now lets say your voltage to the machine is only 455v. Now your secondary transformer will give you less than 240vac. If the transformer for the dc voltage is on the 240v tap then we now have less than 28vdc. On these machines the dc voltage can't be below 25vdc or problems will happen. So many devices on this transformer. I tried to explain the best as I could. Thanks for your help.
Jim
 
Re: Primary wires from the Power Company

James
If this utiltiy is having a peak load during the summer, the regulator at the substation is boosting the primary voltage up. As the load goes down the regulator reduces the voltage.
You may want to check and see if thats the way it works in your location. By the way where are you? I bet the taps on the trasformer are not set
at the center position.

[ June 28, 2005, 07:27 PM: Message edited by: bob ]
 
Re: Primary wires from the Power Company

James - Your utility voltage is varying 455V to 484V on a nominal 480 V service. That's a range of -5.2% low to +0.8% high.

By changing a tap, you will still have the same voltage swings when the load changes but they will be from -1.7% low to +3.2% high. That range is probably better for your equipment and will keep you out of the low voltage problem.

Good Luck.

Bob W.
 
Re: Primary wires from the Power Company

James all electric equipment should handle = or - 10%.

If your equipment can not handle this I feel it is your problem to make the corrections.

Whatever actions you take will have to deal with fluctuations within the = or - 10% range so simple moving taps on a transformer is not the best way to go.
 
Re: Primary wires from the Power Company

Bob, you are correct in what your saying. I live in the Des Moines,Iowa area. When the power company re-feed this Industrial Park they were thinking that they had enough power running this way so they didn't put the regulator in. This is the first year this has all happen with the voltage problems. For the last 10 years the voltage has always hung around 483. They did tell me that they are trying to get a regulator installed back in this area but could take as long as a year. Iwire, I understand what you are saying but why after 10 year should we make all these changes just because the power company didn't figure things correct. I also think that + or - 10% is alot but your correct. I believe 5% is better. Anyway thanks for all your help and if anything interesting comes up I'll let you all know.
Thanks!
Jim
 
Re: Primary wires from the Power Company

Normally, we do not use voltage regulators except for long distances from our substations. If you were behind a set of regulators and are now being fed directly from a substation, the voltage will fluctuate a little more. The electric utility probably had to reconfigure their lines because of load growth and you got stuck.

They will have to order voltage regulators which will take a while to get all the management approvals, the P.O. sent in and the waiting time to get the regulators. After all that, the work order will have to be written and the work scheduled. They can't use the old regulators because they are damaged or have failed, they are in use somewhere else, they were loaded with PCBs, or some other reason. :D
 
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