strange electrical AC problem (high/low voltage)

We are having some problems with the AC in our house and I wonder if some of you can give me some idea what might be causing it.
We first noticed it to be lights flickering, and I thought it might be some neighbor using some heavy equipment or something. Then a few days ago while working on the computer I noticed my DSL modem and router just power cycled for no reason.
So I went out and bought a UPS, and at night during 8-12pm, I can see the UPS kicking in every now and then and goes back to AC power. So something's wrong.
I took out my voltmeter and measured it, much to my surprise, one of the AC lines is 90v and the other is 150v. In my room, one of the lamp is very bright while the other one is dim.
After about 12pm, it sort of gone back to normal, both lines register ~120v.
Could a neighbor using some stupid equipment be causing this voltage drop and increase? Has some equipment in the local electrical company gone bad? The problem is not consistent, sometimes it happens and sometimes it doesn't...
Thanks.
Raymond
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Greetings,
The only way I know to get 150V where their should be 117V is if two 117V circuits on different phases share a common neutral and the neutral has somehow come disconnected or is lose. Before proceeding, please check for this occurrence and let me know what you find. (You can probably check by turning off circuits at the circuit breaker and watching the voltage.)
Hope this helps, William
PS: Surprised your 150V bulb doesn't burn out.

~120v.
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snipped-for-privacy@none.com wrote:

Like Dean said, you have an open neutral, or a high impedance connection somewhere in the neutral. Could be anywhere from the transformer that serves your house to your panelboard. If you have neighbors on the same transformer, see if they have similar problems. If so, you may want to call your power company.
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snipped-for-privacy@none.com wrote:

<SNIP>
Start with a call to the utility. The (intermittent) open neutral may be their problem or might be yours. They will usually check and find out.
Jim
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snipped-for-privacy@none.com wrote:

Everyone is right, but Speedy has the whole story. It is likely a bad neutral, but that could be outside you home. It the problem is in all the circuits in your home it is almost certain to be outside and you need to call the utility. On the other hand if it is only effecting two circuits, it is likely in your home and you call an electrician or if you are comfortable that you can safely work with electrical wiring you should be able to fix it yourself. That fact that you ask however leads me to believe this is a job for the pro.
--
Joseph Meehan

26 + 6 = 1 It's Irish Math
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