60V Single Phase

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ed downey

Senior Member
Location
Missouri
Just Curious If There Is An Easy Explanation For This Situation. Last Night During A Thunderstorm The Power At The House Went Out For A Brief Moment Then Came Back On But We Only Had 60V Single Phase For A Couple Of Hours. Is There A Quick Explanation Of What Could Have Happened On The Utility Side To Create This Situation.
-Ed
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: 60V Single Phase

Tom's cap lock key was on, ;) I think he was trying to point out all the caps in the OP.

[ April 20, 2004, 03:47 PM: Message edited by: iwire ]
 

bennie

Esteemed Member
Re: 60V Single Phase

tHIS iS cAPS lOCK.

This Is Capitalization Of Every Word.

Am I missing the relationship to electricity :eek:

[ April 20, 2004, 04:08 PM: Message edited by: bennie ]
 

bennie

Esteemed Member
Re: 60V Single Phase

Back to the original question; There is a logical explanation for every event. Unfortunately I don't know them all.

I would like to solve this problem, but need more information.

I assume the 60 volts was from line to neutral. Was this voltage on both lines to neutral. What was the voltage from line to line?

Does the distribution transformer have one or two high voltage bushings?
 

ed downey

Senior Member
Location
Missouri
Re: 60V Single Phase

Bennie,

Yes It Was Line To Neutral. I Did Not Check Line To Line Since It Was 4:00 AM And I Didn't Want To Open The Panel At That Hour. I Checked The Voltage With A Fluke 87 III At Three Different Receptacles On Three Different Circuits And All Of Them Read Around 60V Line To Neutral. I Then Opened All The Circuit Breakers That Fed Electronic Equipment. I am Not Sure What You Mean By The Bushings. The House Is Fed From A Pad Mounted Transformer With The Primary And Secondaries Run Underground.
-Ed
 

bennie

Esteemed Member
Re: 60V Single Phase

Thanks Ed: I was thinking overhead service.

The only scenario I can imagine, is losing the MGN between two radial fed transformers. This will place two primary windings in series, creating half voltage on secondary.

[ April 20, 2004, 08:18 PM: Message edited by: bennie ]
 

bennie

Esteemed Member
Re: 60V Single Phase

Fine Charlie, leave me hanging out. I was hoping for some of your knowledge about electricity. :cool:
 

charlie b

Moderator
Staff member
Location
Seattle, WA
Occupation
Electrical Engineer
Re: 60V Single Phase

You don?t need me on this one, Bennie. I am certain that you and Tom already gave the best available answers to Ed?s question, though I think yours is closer to the probable truth.

I have no experience in line work, so I may have this all wrong. But here is my reasoning for agreeing with your explanation:

It is clear from the way Ed worded the question that the problem went away without any intervention on his part. That means it was on the utility system, and not within his own home. I also infer from Ed?s wording that, after he first measured the 60 volts, the power never went off completely again. At some point, the normal voltage was restored, but without an obviously long period of ?no power.? That tells me that the problem was not in the transformer that served his house, for otherwise there would have been a blackout period during its repair or replacement. Therefore, the problem had to have been upstream along the radial, or even at the serving substation.

Given, then, that his transformer was not the problem, but recognizing that its secondary was giving half voltage, that necessarily means that the primary voltage (line to neutral) was half of the normal value. A primary phase conductor cannot do that on its own. But the phase to neutral voltage can vary all over the map, if the neutral becomes disconnected from planet Earth. A loose neutral could explain any strange measurement of voltage within a house. But this was exactly half of the normal value, and that fact is too much to accept as mere coincidence. Your notion of two primaries being placed in series (by virtue of a loss of the MGN connection) provides a credible answer to the voltage being exactly half of normal. I can think of no other.

As Sherlock Holmes is reputed to have claimed, ?Once you eliminate the impossible, whatever remains, however unlikely, must be the truth.?
 

charlie b

Moderator
Staff member
Location
Seattle, WA
Occupation
Electrical Engineer
Re: 60V Single Phase

Many thanks. Please allow me now to indulge myself in a quotation from J. R. R. Tolkien (a line you would not have heard in any of the three LOTR movies): ?Praise from the praiseworthy is above all rewards.? :D
 

bennie

Esteemed Member
Re: 60V Single Phase

Good thing I just had an MRI on my head, it wouldn't fit in the tube now :eek:

I have analyzed this fault a bit further. The MGN, or in this case, likely the concentric neutral, has possible pulled out of the lug in the pad mount next to the one supplying this home in question.

I saw a similar occurrence when an auto hit a transformer and moved it a few feet.
 

ed downey

Senior Member
Location
Missouri
Re: 60V Single Phase

Charlie, Actually I Type Everything In This Way Manually. It Is A Habit I Got In To About 10 Years Ago And Now I Find That It Is Harder For Me To Type Without Capitalizing The First Letter Of Every Word.
I'm Just Strange What Can I Say!
-Ed
 

ed downey

Senior Member
Location
Missouri
Re: 60V Single Phase

Here Is The Reply I Got From Westar Energy When I Sent Them An E-Mail About The Situation:

Mr. Downey,

Thank you for using our web site.

At 3:30am on April 20th, a breaker opened momentarily due to the weather,
which
then caused a pole to catch on fire. Your phase was dead and the reason you
had
60V is due to voltage coming from a transformer bank/backfeeding. When you
are
aware of the low voltage, it is best for you to turn off the main breaker
in
your home to avoid damage to electronic equipment.

Please let us know if we can be of further assistance.

Sincerely,

Theresa
Customer Service

I am Not Sure I Completely Understand The Response About The Backfeeding Due To A Pole Catching On Fire Though.
-Ed
 

mattmulka

Member
Re: 60V Single Phase

This would be a lot easier if I could draw this out for you....

Somewhere between the utility substation and your transformer (or the downfeed to your transformer if you are on an underground loop) the phase feeding you became open (like, say, due to a pole fire). However the other phases remained intact.

Past the open there was a three phase transformer bank with a delta primary. Your phase was being backfed through the primary of that transformer. That's what gave you the 60 volts.

I hope I helped clarify this. Remember, always test for backfeed!!
 

loren

Member
Re: 60V Single Phase

You may need to rethink this a little. The neutrals are all tied together. Primary and secondary as well as ground rods at the transformers. That would mean that if you lost the primary neutral the secondary would step up.

Most feeders leaving a substation are fed from a Wye secondary. These are usually set up with multiple coil windings making up each phase. These windings are tied in series most of the time but can be connected in parallel through tap changers. Or vise versa. It would be my GUESS that this is what happened.

You may want to call the local power facility to find out just what did happen. Contact the outage engineer for your area.
 

msd

Senior Member
Re: 60V Single Phase

What about a neighbors illegal generator hookup that is backfeeding the utility, and you.

Maybe voltage drop is 50% by the time it gets down the block to your house from his gen-set.
 
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