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technical question about brown outs and power co. distribution

Posted by davidrt28 (My Page) on
Wed, Jan 9, 13 at 5:42

I feel like power companies are taking their responsibility to provide reliable, safe power less and less seriously. I live in a semi-rural area (but not far from a semi-urban one) and it seems like the past couple years have been plagued by ridiculous surges, brown-outs and random interruptions unrelated to storms.
Back in the spring I had a brown out to 60V for over 5 minutes. I saw the voltage read out on my computer's UPS. Incandescent bulbs were dim and amber and my ceiling fan comically slowed down. I immediately unplugged my fridge because it's my understanding that can destroy their motors in short order.
Here's my question: I called the power company to complain about this, and they said they'd send someone out. At the door he said it could be a problem with "a ground" and that he would check them. I think the pole transformer is at the other end of the street about 1/3 mile away, I thought he meant he'd check that transformer. The next day I noticed he'd dug up MY ground rod and stuck it back in the ground. WTF?
My understanding is the center tap of THEIR transformer divides the two legs of the 240V phase. Did they actually send out a lineman who doesn't understand how electrical distribution works, or do I not understand it? Their 120V A & B legs should be 120V w/respect to ground and with respect to the neutral they also send into my house, right? I don't see how my ground can possibly have anything to do with it. If it wasn't working at all, that would cause a safety problem in my house, but how could the voltage come to be so reduced? If a shorted panel caused leakage into ground enough to lower the voltage to 60V, the main breaker would have to fire immediately.
Please feel free to correct me if I'm misguided, but I'm reading this as "we know we had a faulty transformer or transmission problem, but we wanted to do some smoke and mirrors at your house to make you think it wasn't entirely our fault." BTW at best he got the ground rod 2-3" deeper. Hardly enough to make a 60V difference LOL. Nor did my lights dim again to 60V when he was "working" on it.

Would 1 phase of their multiphase distribution going out cause such a brown out? In my research into it, I don't think it could under normal circumstances - my understanding is any given single phase circuit usually relies on just one of the incoming feeder's 3 phases. But again I could be wrong.

This post was edited by davidrt28 on Wed, Jan 9, 13 at 6:29


Follow-Up Postings:

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RE: technical question about brown outs and power co. distributio

Unsticking this, but respond to either thread.


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RE: technical question about brown outs and power co. distributio

Most pole transformers are line to neutral loads on the higher voltage distribution system (7.2 kV being a common level).

A few are line to line.

If you are on a line-to-line pole transformer a dropped distribution line would cause the voltage to fall.


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RE: technical question about brown outs and power co. distributio

Thanks brickeyee.


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RE: technical question about brown outs and power co. distributio

One more interesting bit of info. As we know, "automatic" means "can malfunction"...surely one of the recognized corollaries to Murphy's Law.
from http://en.wikipedia.org/wiki/Mains_electricity

Voltage regulation

To maintain the voltage at the customer's service within the acceptable range, electrical distribution utilities use regulating equipment at electrical substations or along the distribution line. At a substation, the step-down transformer will have an automatic on-load tap changer, allowing the ratio between transmission voltage and distribution voltage to be adjusted in steps. For long (several kilometers) rural distribution circuits, automatic voltage regulators may be mounted on poles of the distribution line. These are autotransformers again with on-load tapchangers to adjust the ratio depending on the observed voltage changes.

Here is a link that might be useful: http://en.wikipedia.org/wiki/Mains_electricity


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RE: technical question about brown outs and power co. distributio

Complain to your local public utility commission.


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RE: technical question about brown outs and power co. distributio

FWIW, since they were in the neighborhood, we haven't had a prolonged brownout of the type I described. I think something was wrong elsewhere (besides my ground rod!) that they fixed. When I made the above post, those sort of long, multi-second or even minute brownouts had been on-going for at least a year, perhaps every other month.

We still have had a couple random brief outages or surges of 1-3 seconds.


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RE: technical question about brown outs and power co. distributio

"We still have had a couple random brief outages or surges of 1-3 seconds"
Squirrels jumping on transformers can do this. Or the tip of a tree branch hitting the line momentarily. The POCO cannot control squirrels-- and people complain about tree trimming. I know at least one city that adopted a tree trimming ordinance that limits what the POCO can do. In this area, the POCO calls the grounded conductor in their distribution lines the neutral-- but it is grounded. A loose neutral on the secondary of the distribution transformer can cause fluctuating voltages at the customer's premises-- as low as 60 volts or even lower.


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