🚀 go-pugleaf

In article <1990Jan11.015852.7031@phri.nyu.edu> roy@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.  I know it is possible to make a synchronous motor
>have a leading power factor with proper external excitation, but have no idea
>how often that is done.

Actually, by the time you get to a 500 kv backbone or to a generating
station, the PF is pretty close to unity.  I'd have to get some of my
books out to refresh actual numberes.  At the hub where I trained,
we handled something on the order of 12,000 megawatts.  Seems to me
like the megaVAR recorder only went to 20 MVAR or so.  Generators 
are typically run a bit over-excited in order to feed some leading
VARS down the line and cancel inductive VARs in the distribution
system.  As I mentioned in an earlier post, PF correction is generally
taken care of on a local basis.  The reason is simple.  Because of the
sheer size and the resultant limitation on engineering margins of,
say, a 5000 MVA 500 KV transformer, it is important that it handle 
high PF power.  One can easily engineer 2 or 3:1 safety margins into
pole pigs.  Not so with these behelmoths.

>	Now, for another question.  A while ago, I was wandering around in
>the basement, looking at the power connections.  No, not my basement, where I
>work basement.  The building engineers are wonderfully lax about not locking
>doors.  Anyway, behind the panels with the 5000 amp breakers were a couple of
>rather ordinary-looking electric meters and boxes with wire seals on them.
>Some of the boxes said "Con Edison" on them, which seems normal, but some of
>them said "New York Power Authority" which got me curious.  Why would the
>NYPA have a sealed box in a not-particularly-special building in Manhattan?
>What's in that box?  Could the NYPA actually be interested in the few measly
>MW our building must draw?  Isn't that sort of like the Federal Reserve
>worrying about whether my personal checkbook gets balanced?

Judging by the breaker sizes you quote and looking at your address, I'm
assuming your building represents a significant load.  Most likely, the
sealed box contains load shedding equipment that allows NYPA to shed 
non-essential loads like A/C during power emergencies.  Did you notice
phone wiring going to any of these?  Other common instrumentation is
real-time telemetry so that the utility can observe usage patterns.  It
is very common to contract for a certain pattern and to charge more
for or even shed loads that significantly deviate from the contract.

One other note.  I've done at least a little bit of almost everything
a line crew for a utility ever has to do, including working 181 KV
lines hot and climbing around energized 500 KV yard structures.
Yet the thing that scares me the most is to be in a customer equipment
vault as you've described.  I've seen the aftermath of more than 
one breaker panel explosion.  I had a close friend critically burned
when he operated the handle of a 5000 amp, 480 volt breaker and it
exploded.  I'm as nervous as a whore in church in these places.
I'd advise you make your "yard and dock" tours rapidly :-)

John

-- 
John De Armond, WD4OQC                     | The Fano Factor - 
Radiation Systems, Inc.     Atlanta, GA    | Where Theory meets Reality.
emory!rsiatl!jgd          **I am the NRA** |