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From: irwin@uiucdcsb.cs.uiuc.edu
Newsgroups: sci.electronics
Subject: Re: How are power line voltages determi
Message-ID: <162700012@uiucdcsb>
Date: 11 May 88 17:29:00 GMT
References: <5770004@hpscdc.HP.COM>
Lines: 25
Nf-ID: #R:hpscdc.HP.COM:5770004:uiucdcsb:162700012:000:1389
Nf-From: uiucdcsb.cs.uiuc.edu!irwin    May 11 12:29:00 1988


I may be able to shed some light on your question. Years ago, I worked
for Illinois Power Co. The Illinois Commerce Commission is the one that
sets the standards as to what is acceptable, in our state.

The current minimum acceptable voltage to the customer is 113 VAC and
the maximum is 127 VAC. Since the mean value between the two is 120 VAC,
that is what should be stamped on electrically operated devices, designed
to be operated at the current standards.

Many moons ago, 110 VAC was the standard and though it is no longer
acceptable, old habits die hard and people still refer to "110/220".

I do not believe there is a federal standard, probably a state standard
in each state, and are also probably all the same, because of the link
of utilities nation wide, forming a "power grid". Utilities purchase/sell
power to each other, and the study of the grid is an interesting subject.

When it gets dark on the West coast, people to the East have gone to bed
and a lot of the lighting load is shut down, so, power flows to the West
through the grid. As people in the East are turning on lights, it is still
light in the West, so power can flow to the East. This grid has been known
to have its problems however, as there have been times when several states
were put into the dark with a massive failure. Safeguards are built in,
but, it still can get into trouble from time to time.