Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!gatech!purdue!i.cc.purdue.edu!j.cc.purdue.edu!pur-ee!uiucdcs!uiucdcsb!irwin 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.