Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!cs.utexas.edu!tut.cis.ohio-state.edu!pt.cs.cmu.edu!sei!rsd
From: rsd@sei.cmu.edu (Richard S D'Ippolito)
Newsgroups: sci.electronics
Subject: Re: Watt Hour Meters
Message-ID: <5606@ae.sei.cmu.edu>
Date: 11 Jan 90 16:15:25 GMT
References: <1990Jan11.015852.7031@phri.nyu.edu>
Reply-To: rsd@sei.cmu.edu (Richard S D'Ippolito)
Distribution: usa
Organization: Software Engineering Institute, Pittsburgh, PA
Lines: 35

In article <1990Jan11.015852.7031@phri.nyu.edu> Roy Smith writes:


>	Anybody know what the total average power factor on the power grid
>is?  I would imagine it must be massively lagging, what with motors and
>transformers being most of the load.  I can't think of any typical capacitive
>loads on the power grid.  

Small utilities have banks of powerfactor correction capacitors which they
manually switch in and out -- larger ones have gone to reactor sets switched
automatically by thyristors.  Large industries also do the same.  Rotating
machines were more common in the past.

The average depends on the limit settings in the utility's reporting
equipment (mostly software) and the alertness of the operator.  Bank
switching too often lowers the life of the equipment and causes line
transients, which is why the thyristor controlled units are preferred.  Of
course, they cost a lot more -- it's an economic decision, as all utility
decisions are.  Typically, they keep it to within 10% of unity either way.


>I know about ELI the ICE man, but that's a pretty bad mnemonic because you
>can interpret either way!

You may know the phrase, but you certainly don't understand its
interpretation.  The order of the letters is the key.  Voltage (E) across an
inductor (L) leads (comes before) the current (I).


Rich
-- 
Hitting baseballs and writing software are two professions where you can
become a millionare with a 75% performance failure rate.
							 rsd@sei.cmu.edu
------------------------------------------------------------------------