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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics
Subject: Re: Power System Frequency Keeping
Message-ID: <1755@kitty.UUCP>
Date: Sun, 10-May-87 13:08:24 EDT
Article-I.D.: kitty.1755
Posted: Sun May 10 13:08:24 1987
Date-Received: Sun, 10-May-87 18:56:03 EDT
References: <9779@decwrl.DEC.COM>
Organization: Recognition Research Corp., Clarence, NY
Lines: 32
Summary: Local monitoring is also performed...

In article <9779@decwrl.DEC.COM>, white@cogito.dec.com (Robert V. White MLO6A-3/T96 223-7647) writes:
> >	A good question to ask is "with all these random (albeit
> >synchronized) generators all over the place, what's to keep the grid
> >frequency from drifting?"  The answer is that somewhere on the grid,
> >somebody is monitoring the line frequency, and comparing it to a standard
> >(WWV, probably).
> 
> I believe that the monitoring is done by American Power Corporation in 
> Canton, Ohio using a Cesium time standard.

	I believe that most power plants also maintain a local frequency
standard, with a long-term deviation recorder.
	I have seen such devices in fossil-fueled plants (I have never been
in a hydro or nuclear plant).  There is a strip-chart recorder which
continuously records +/- deviation from 60 Hz.  In one plant that I saw, the
reference frequency was provided by a Tracor frequency standard with a WWVH
receiver.  There is apparently a certain amount of local power plant
"leeway" in providing frequency compensation to assure long-term 60 Hz
accuracy; i.e., the local plant can operate "off frequency" to a limited
extent (fractions of a Hz) in order to provide compensation, with such off
frequency compensation still not resulting in excessive power loss to the
grid. 
	Frequency compensation is usually provided during off-peak hours.
The algorithm is simple: the minus deviation is continuously integrated
and compared with the plus deviation, and once a day during off-peak hours
a compensating deviation is computed to run the plant for a given period of
time at a given frequency.

<>  Larry Lippman @ Recognition Research Corp., Clarence, New York
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