Acceptable Voltage Variations ???

[richwaskowitz]

I have a customer with a new tanning salon fed with a 200 amp 240V 3 phase service. They are experiencing voltage swings between 216 and 260 volts depending on the time of day and day of the week. There is a noticable difference in the light output of the beds at the low end and overheating and component failure at the high end. I had the power company install a data logger for over a week in hopes that they would record the problem and address the issue but they are claiming that these numbers are within acceptable limits. I have no way of disproving that. The manufacturer of the beds will not warranty their products at these voltages. Except for installing voltage regulators or constantly changing connections on the buck-boosts, what can be done (economically)?

 

[bphgravity]

Re: Acceptable Voltage Variations ???

I believe a typical utility company is required or will at least try to stay within + or - 10% of the nominal supplied voltages. In most cases, equipment will not be greatly effected by that variance. Your situation may be an exception.

I would say that if you have specialized equipment with specialized electrical needs, then it would be the owners responsibility to provide power quality conditions and equipment and not necessarily the utility company.

 

[pqtest]

Re: Acceptable Voltage Variations ???

Hello Rich,

Depending on what State you live in, this can get complex pretty quick. I?ll use Washington as an example since my company is based up here.

First, you need to determine if the electrical utility provider in question is regulated by your State Utility Commission, or whatever you happen to call it where you live. In Washington, electrical services providers fall under what we call the Utilities and Transportation Commission (UTC), and we have only 8 providers Statewide.

Next you have to dig through your State regulations. Here, regulated utilities fall under Washington Administrated Code (WAC) 480. In our case, the WAC exempts 5 of the 8 utilities from having to comply with the WAC rules. (PUD, co-op, etc?)

WAC 480-100 then outlines the minimum voltage compliance standards: No frequency deviations from 60 Hz under normal conditions, voltage fluctuations of plus or minus 5% of the adopted voltage, and a total voltage variation from MIN to Max value may not exceed 8% of the standard adopted voltage, as well as several other requirements.

There are of course various exemptions for emergencies and natural disasters.

The 5 exempt utilities could have specifications that are more relaxed then the WAC requirements, (that is, of poorer quality) and the customers would really have no recourse.

If the 3 regulated utilities get too far out of tolerance, then a complaint can be filed with our UTC.

My answer to your question is, take a look at your State rules to see if they really are in compliance or just passing the buck. If they are a regulated utility, I?m pretty sure your State will have minimum performance requirements.

The description of your tanning salon customer shows a utility deviation of plus or minus 10% from nominal, 20% total variation- are the tanning beds themselves running on 120 Vrms or 240?

If they operate at 120 Vrms, a 10% drop would go down to 108 Vrms- any chance you can get the utility to install their voltage recorded at the electrical receptacle for the beds for more accurate readings?


Best of luck,

Mark

 

[hurk27]

Re: Acceptable Voltage Variations ???

Another thing to watch out for is make sure that the meter that your using is a true RMS meter. Like a fluke. anything else will give you erroneous readings because of other factors in the circuits you are trying to read. But what Mark has said is true for most states and here in Indiana they have to adhere to the +/- 5% or 10% over all.

If the state does not have any requirement's then as been said you might have to tell the operator that they have to invest in a power line conditioner which for this place can be quite expansive. As I know tanning beds can be voltage sensitive to high voltage swings. There are several manufactures that can provide the type of power conditioners for your need.

[ September 02, 2004, 01:51 AM: Message edited by: hurk27 ]

 

[richwaskowitz]

Re: Acceptable Voltage Variations ???

Thanks for the input. This public utility (Detroit Edison)is regulated by the gummint and we have enlisted the services of a consumer advocacy group. We have not however asked specifically for any published limits. We will do so.

For now, all I can recommend for the salon is to determine what the average voltage is (and that has been established using the power company's data logger over several weeks) and adjust the buck-boosts to supply the beds with the manufacturer's recommended input voltage. Seeing as how just about all the beds I have every encountered have ballasts that come from Europe, they all require 220, not 240 volts, requiring the buck-down. I think that the cost of regulators would be prohibitive.

Can anyone recommend a regulator for this application? They have 6 beds at around 20 amps and 2 at around 60 amps.

 

[brian john]

Re: Acceptable Voltage Variations ???

In our area both public utilities will supply in writing there acceptable limits.

Utilize a decent recording disturbance analyzer and monitor at the service and at the loads for a set period of time or till the end user has a problem.

The low voltage may be a by product of the loads and the high voltage could be a byproduct of the time of day use or both

1. Does the end user have a step down transformer in their facility?
2. How many customers are on the trnsformer?
3. Are the high voltages surges or impulses?
4. Are the low/high voltages time related?
5. Do you have documentation to support your accusations?

 

[richwaskowitz]

Re: Acceptable Voltage Variations ???

This is in answer to your questions....

1. Does the end user have a step down transformer in their facility? No. A pole mounted bank supplies the whole block.
2. How many customers are on the trnsformer? At least 10 if not more.
3. Are the high voltages surges or impulses? These are sustained over and under voltages lasting hours, not spikes.
4. Are the low/high voltages time related? Absolutely. The voltage goes up after "business" hours and drops during them.
5. Do you have documentation to support your accusations? Yes. We have the print-outs from the data logger.

Another bit of info I did not provide earlier is that these voltages are not effected by the load at this site. The same readings can been seen with or without any sigificant load on our end.

It sure looks to me like a classis overloaded distribution system.

 

[brian john]

Re: Acceptable Voltage Variations ???

I'm sure you have done this but

Get a copy of the local utility terms of service

Contact your local utility representative

It has been my expireence that the utilities will work with you to resolve and issue concerning their service should the service not meet published specifications.

 

[charlie]

Re: Acceptable Voltage Variations ???

Rich, the electric utilities in Michigan are very closely regulated by the state. Go to the State of Michigan's web site and do a search for the regulations (probably under the utility commission's rules). I assure you that the state sets the limits of their voltages and amount of flicker that they are permitted to have.

I am betting that it will be much easier to get the information from the state than from Detroit Edison. I am saying that because the average person you deal with at any electric utility only knows the basic rules and have no idea where they are written. If you get to the right person in the engineering area, they will be happy to provide it to you but it will be difficult to locate the right person.

 

[hurk27]

Re: Acceptable Voltage Variations ???

With that many service's on one set of transformers it sounds like the POCO boosted the voltage to 260 volts to over come the load and voltage drop. But this creats a big problem when this load drops off at nite. The voltage will go back up to the set tap voltage. Sounds like the POCO just kept adding customers to an exsisting transformer bank rather than install new transformers. We had this problem in Florida out in the sticks as the voltage drop was bad and as load droped off the voltage would rise. and Lee County Co-op would boost the voltage but this would only cause an over voltage at nite.

Of course this might not be what is happing at the tanning salon. But somthing to ask about?

 

[charlie]

Re: Acceptable Voltage Variations ???

Wayne, it is very rare that an electric utility would even think about changing the taps on a pole mounted transformer (which is not to say that it is never done). The reason for that is that external tap changers are an extra cost and are not normally necessary. It is normal to continue to add customers to a transformer bank and if it done by the service connection department instead of engineering, no tests are ever run to see if the bank is overloaded. Under these conditions, the voltage will definitely raise when load is dropped off in the evening hours.

Wayne, I am guessing that you are correct about the load issue and it will be resolved after a test on the bank is done. The first step is to get a voltage test on the service and then the electric utility will follow up with a load test on the bank.

 

[hurk27]

Re: Acceptable Voltage Variations ???

I agree as the only time voltage should be raised to over come a voltage drop is when a known load is applied. I went around several times with Lee County Co-op over this and they would just say " We always have done it this way" Well maybe in the past when there wasn't as much electronic loads that could be damaged by over voltage but to do this today could cost them allot. There was another post not to long ago the person was in South America somewhere that had said the POCO down there said they could do this to over come a long run. But I told him that it wasn't a good idea. The only proper way to over come voltage sag is to have the properly sized transformer's with the properly sized service conductors adjusted for the length of the feed.
As for the reading of 260 volts in non-peek hours this is the only thing that I could think of that would cause it.

[ September 06, 2004, 04:46 PM: Message edited by: hurk27 ]

 

[charlie]

Re: Acceptable Voltage Variations ???

Sorry, I didn't read close enough to realize it was a co-op. A lot of co-ops and municipals (not by any means all) do some really weird stuff and they are not usually regulated. I am forced to back down from logic and bow to the superior knowledge of the situation.

 

[hurk27]

Re: Acceptable Voltage Variations ???

weird Isn't the word for it.

But as for "superior knowledge" No way, I'll stick to the low voltage stuff. You can play with that stuff that makes your hair stand on end without touching the wire. maybe thats why there voltage is not too stable. :roll: