voltage fluctuation on one leg of service drop

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Jack Edwards

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West Tennessee
I am currently at wits end with a fluctuating voltage drop on one leg of a 120/240v single phase service. The fluctuations from 65v to 125v occur only on one leg the other leg is a rock steady 120v. The grounding electrode system checks out good. The local electrical company servicemen have checked the service drop and transformer and say they are in specs. They have witnessed the fluctuations using their own meters at the meter base. They say there is nothing wrong on their end. These fluctuations last for several minutes then may go away for minutes, hours or days and on a random basis. I say there must be something wrong with the transformer---- Any Ideas??
 
Call the electric utility back and insist that they install a recording voltmeter on the service for a week. Tell them that you have an intermittent problem and an instantaneous reading will not cut it. If they balk, call again and ask for the power quality or distribution engineering department and tell them what has happened. Also, document who you have talked to and when the conversation took place. :smile:
 
I would start with redoing the taps. If that doesn't do it follow Charlie's advice and insist the POCO performs a week long PQ test. I'm not sure where you're at but I'm in the Phila. area and have connections with the local utilities here.
 
Thanks for the info and all was along the lines I was thinking. The fluctuations the electric co. guys observed were some of the extremes I saw. They did redo all the taps and changed all the ones on the drop from screw type to crimp-on. This service drop runs for several hundred feet converting from a twisted wire off the transformer to a standard power line configuration across the property and back to a twisted wire drop from the last pole to the service head. I walked the entire line with them and no limbs or other obvious problems with lines. The electric company is a small co-op in West Tennessee and the response I get is "Duh--Idonno. If our stuff checks out it must be your problem." from the manager. I suspect may have a drop conductor that is bad (partially broken inside insulation and separating with wind) or a transformer problem. My next stop is the state electric commission.
 
I have a commercial customer who was experiencing voltage drop in the summer under heavy loading. This was due to an aerial run that was too long from pole mounted pots. I knew what the problem was before the utility trouble guys even showed up. They spent the whole day there and concluded the same, however their engineering department attempted to stall moving the pots to a closer pole. The trouble guys were ashamed of their own company.

So my customer gave me the go ahead to bring in a portable generator. When I called the utility back I told them we had the store running on a generator and the company had turned the matter over to their legal dept.

They were there the next day to fix the problem.
 
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