Strange power failure at the house this morning.

[uglyboywith11fingers]

Hope this is appropriate for this forum, after all, we are rural.
This morning I was out in our attached garage, using my air nailer/stapler to slap together some free-standing shelf units for my daughters basement storage area.
The air compressor (120v) kicked in, then started to stop & start and finally just buzzed. I quick like a bunny hit the switch, and started to scratch my head, when wifey burst into the garage from the house, telling me the computer was popping and fizzing and smoking. Into the house I go, smells like burnt electronics, so I grab my multi-meter to check the power. One phase is at 147volts, the other at 93volts.
I quick went for the main switch. After thinking about it for a minute, I opened the main switch box, and checked things out with the multi-meter. with the main sw. off, both phases are at 120v. Turned on the main sw, back to the 147 & 93 situation... so I left it off & called the power company.
Well, they checked things out & tell me they think the problem is with the underground service wiring from meter box to the transformer at the road... about 200 feet.
Likely a problem with the neutral, they say. They say that repeated frost heaving over the years (house built in mid 1960's) has probably damaged the wiring, they suspect the conductors may be direct buried, not in a conduit. They are in a metal conduit going into the ground from the meter box. 100 amp service, by the way.
They left me with some neat transformer/gizmo attached at the meter box which apparently can stabilize the power even if one of the conductors, hot or neutral, is completely open.

So, we have power again, and a different crew is scheduled to come out and further diagnose our predicament. So far, 2 PC's dead, laser printer dead, digital light timer dead.


So I have a couple questions for you power experts on the forum...

1. What do you think of the diagnosis so far ? A few years ago, my neighbour across the road who is on the same transformer, had power fluctuations that required the utility to replace the Y crimp-connectors up at the transformer, that connect both our houses to the transformer. Apparently an overheated connection. At that time we had not noticed any power fluctuations. My limited knowledge would lead me to suspect a bad connection somewhere rather than a sharp rock or something underground intruding on the service wiring.

2. I'm in Ontario... who is usually responsible for repair/replacement of this underground service wiring if that is the problem ?

thanks for any opinions,

Pete

 

[Jim Nelson]

We had pretty much the same thing happen at our last place but it happened when nobody was home.We lost the air conditioner but that was all.Ours was direct burial aluminum and the power co. guy said it was pretty common.They fixed us up with one of those transformer gizmos temporarily and replaced the whole thing from the transformer to the box a week or so later.They allowed partial payment for the new ac but I don't remember how much.The replacement was copper in conduit.
This was in California so I don't know what they will do for you up there.

 

[PILOON]

Saw a similar condition on a house renovation that I was monitoring for the owners. (in Quebec)
The job called for a sub panel for the new circuitry and work was performed by proper electricians.
While not an electrician myself I perhaps know much more than most as I am licensed in aviation electrics and actually did wire my entire house (under a certified electrical contractor).

My 3 1/2 digital meter showed that same type of voltage variations as mentioned above. They at first claimed that +/- 10 volts in either direction was normal and acceptable, but norms were exceeded.
Hydro after having sent 2 different crews and doing all sorts of tests simply added a new transformer for that one client as they could not locate the cause.
The client in turn claimed that she was short changed as the meter was reading the high side and she was getting less than paid for. She won and was credited a fair amount.

However in her case all wires were airborne to her meter so all lines and connections were the power co. workmanship.

Underground I suspect was not done by hydro as usually they terminate at a pole.

 

[s219]

I'm not an electrical expert by any means, but if the two legs showed 120V when the main breaker was off, but then went to 93/147 with the main breaker on, it suggests to me that something inside the house -- probably a 240V appliance or other 240V circuit -- is messing something up. But I suppose it could just be that the home and it's circuits/loads is simply completing the loop to "show" the problem caused by the bad feeder wiring.

What I might do, if there is no risk, is put the voltmeter on and then flip off breakers for individual 240V circuits until the 93/147 goes back to 120/120. Then troubleshoot that circuit by unplugging or unwiring it's load to see if that's the problem.

 

[SPIKER]

You can help it out by making sure you have a good ground rod and neutral tied at the panel. Yes it is common (I have seen it a few times myself.)

Make sure new service it inside the conduit and all should well out last you.

Mark

 

[uglyboywith11fingers]

I'm sorry... I should have mentioned earlier that the first thing the power company workers did was pop the meter, and place a diagnostic gizmo into the meter base, completely disconnected from the house wiring. It had 2 voltmeters, each showing 120 volts initially. Then he switched on a built-in load on this gizmo, and the 2 meters went to the 147/93 situation. That is when they offered their assessment of the problem, something wrong with the neutral back to the transformer.
The problem is NOT in the house.

Pete

 

[cqaigy2]

Had a similar problem when the ground/neutral got damaged.

 

[Mendonsy]

I suspect that the power company's diagnosis is exactly correct.
One of the risks associated with having a remote transformer is that there is a potential for problems in the wiring between the transformer and the distribution panel. Unfortunately an open neutral connection can do more damage than anything else because it will do exactly what yours did. You will most likely have to replace that wiring.

 

[MoKelly]

Probably a foolish question but, would a good surge protector have saved your equipment?

MoKelly

 

[Soundguy]

A power conditioner might have.