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Utility regulation for voltage range - extended overvoltage ?

Utility regulation for voltage range - extended overvoltage ?

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  #1  
Old 01-05-15, 07:35 PM
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Utility regulation for voltage range - extended overvoltage ?

I am experiencing extended, frequent overvoltage (above 130V).
I was just wondering what the utility is required to provide.
 
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  #2  
Old 01-05-15, 08:14 PM
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Most utilities provide power +/-10% of nominal voltage.
 
  #3  
Old 01-05-15, 09:35 PM
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So, nominal 120V. Going up to 132V?
 
  #4  
Old 01-06-15, 01:37 AM
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Depending upon the size and location of your utility's distribution transformer the voltage should hold to much closer tolerances than the full +/- 10% allowable. Since you are measuring only one side of the 240/120 volt supply it IS possible that the other side is dipping in voltage by the same percentage amount as the measured side is rising. This is normally caused by a poor connection of the neutral conductor and that poor connection could be anywhere from the transformer to a multi-wire branch circuit in your home.

Call the utility's 24 hour trouble number, tell them your story and request that the connections on the utility side from the transformer to the meter be tested. When the crew arrives try to get them to also test the connections to your main circuit breaker as well.
 
  #5  
Old 01-06-15, 01:31 PM
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Is it causing a problem, or something you happened to notice incidentally? Other than Edison bulbs, pretty much everything runs better on a slightly above-nominal voltage.
 
  #6  
Old 01-06-15, 04:22 PM
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The way I noticed the issue is that my UPS's are constantly on power trim.
I could increase the voltage. But didn't want to do it just like that.
Not sure if it has a negative impact. Just doesn't feel right considering that the power is bad. That is the reason why I need so many UPS's to begin with.
 
  #7  
Old 01-06-15, 04:37 PM
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Have you checked to see the voltage on the other leg of the panel? If it is low by the same amount as the other leg is high you have a loose neutral issue.
 
  #8  
Old 01-06-15, 06:00 PM
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Is the voltage ever less than 124 volts?

I am not sure how prevalent this still is but years ago, power companies would set the pole transformer voltage a little on the high side so at the far end of the line under heavily loaded conditions the voltage would not be too low, like not be less than 108 volts.

What is needed is heavier feeders along the poles and/or a higher wattage pole transformer (or splitting the houses onto an additional pole transformer). Until then considerable voltage drop (representing wasted energy) occurs in the feeder during heavy load hours of the day.
 
  #9  
Old 01-06-15, 06:25 PM
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The lowest I am seeing in my log file is 123.1V.

I am going to check the legs one the next overvoltage. Usually, happens during the day.
 
  #10  
Old 01-07-15, 09:51 AM
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I checked today. The difference between the two phases is only about 2V. Today I am measuring 132V on one leg and 130V on the other.
Should I call the utility?
 
  #11  
Old 01-07-15, 12:01 PM
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I wouldn't bother -- you're within 10% of 120V and not having any adverse effects from it. It's a little high now, but may drift down a little throughout the year depending on the system load. As long as there aren't corresponding power quality issues like flickering, spikes or notches I really don't think it's a problem.

What kind of UPS do you have? If it's transferring to battery all the time then you should open up the voltage range to prevent excessive wear on the switches. Otherwise the AVR will just take care of it in a constant sine output unit.
 
  #12  
Old 01-07-15, 02:17 PM
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Is there any pattern as to when the voltage goes high? Something like after nine AM and after seven PM? Is it significantly lower from about seven AM to nine AM and four PM to seven PM? If yes, this would point to a smaller distribution transformer and/or quite a few homes on a single transformer. The utility has to set the unloaded voltage on the high end to prevent a low voltage condition under times of peak usage.
 
  #13  
Old 01-07-15, 04:21 PM
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I have APC SUA1000 UPC's. I need to check whether they use battery for power trim or not.

I was going to say that I see the issue during the day. 9am - 5pm.
 
  #14  
Old 01-07-15, 04:57 PM
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Those hours are when the majority of people are not home, adults at work and children in school. Little use of large loads such as electric water heaters or electric kitchen ranges. This sounds to me like the utility placed their distribution transformers in a way that each one serves too many houses and is also marginally sized. Probably not much that you can do about it.
 
  #15  
Old 01-07-15, 05:51 PM
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That explains why the transformer for our sub-division blows up regularly once each summer... I am in a Chicago suburb where I am assuming electrical peak is during the summer. Most heat is gas.
 
  #16  
Old 01-07-15, 07:18 PM
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It would be interesting to know what the voltages run during the summer months when air conditioning is the major load during the day.
 
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