Hey, I'm really glad I read this post. The subject line was the
same one I gave it when I wrote to the list the other day,
Moderating You Off the list. So, I have been ignoring some of
the posts with the same subject line since then. I have also
changed the subject line of this post to more accurately reflect
the topic and what it's about. Thank you for the most
interesting information about the power grid. I wonder what it
will take to really make a "smart grid?" And then there's all the
renewable stuff even people's solar panels, wind generators etc.
What happens to the grid when you feed power into it from all
these separate units? Jim WA6EKS
----- Original Message -----
From: Ron Miller <[log in to unmask]
To: [log in to unmask]
Date sent: Mon, 20 Aug 2012 19:16:38 -0400
Subject: Re: Moderating you off the list!
Martin,
That is very interesting. I didn't have a clue about this.
Ron Miller
N6MSA
Dunedin, Fl.
USA
SKYPE: arjay1
-----Original Message-----
From: For blind ham radio operators
[mailto:[log in to unmask]]
On Behalf Of Martin G. McCormick
Sent: Monday, August 20, 2012 9:16 AM
To: [log in to unmask]
Subject: Re: Moderating you off the list!
The power grid is pretty much what you describe but it is
surprisingly complex, also.
As a student in the late seventies, I had a part-time job
involving
the development of instructional materials for the training of
power line
workers. Somewhere along the way, we discussed what has to
happen when you
connect an AC generator to the grid or more accurately, the
grids.
We have more than one large power network in North America
which
includes the United States, Canada and Mexico.
A very large grid runs all the way from Quebec and New York
State
all the way across the nation to the Rocky Mountains and down to
Texas.
There is a Western grid from the Rockies to the West Coast
and then
Texas has its own grid.
This is based on what I learned in the seventies and it
could be
that some of these grids have merged. Here's the problem. You
know how, in
radio, you can tune a transmitter to the exact same frequency as
another
transmitter and they are said to be at zero beat. These
generators are just
extremely low-frequency transmitters. When you start one up, it
may be a
cycle or two too fast or slow and its signals will beat with the
rest of the
grid at some low frequency like two musical instruments that
aren't quite in
tune.
You may wonder how they connect AC generators in parallel.
After
all, they do it all the time and here is where theory meets
practice.
The word heterodyne means to mix forces. If two people are
on a
tandem bicycle, they must both peddle at the same speed or
nothing much good
happens. Generators are like motors, so much so, that a motor
can be a
generator under the right conditions and vice versa. If you have
two AC
generators running at the exact same speed, you can connect them
together
and they will run as one. The trick is making them run exactly
the say
speed.
What they have to do is connect an instrument to both
generators
that can tell when both are close to being in phase.
When they are, it is safe to hook them together.
When you do this, they keep each other in phase because if
one tries
to lag a little, the energy from the other will force it back to
speed. It's
just like the tandem bike.
If they have to take a generator off line, they disconnect
it from
the grid, first and then they can safely stop it.
Think about this. In New York City, you could put a mark on
the
armature of a generator at a power plant and do the same thing on
a
generator in Oklahoma City and come back a week later and find
both marks in
the same relationship to each other that they were when you made
them
because all the generators in the Eastern grid must phase lock
with each
other or terrible things will happen. I'm talking about
destroyed equipment
and lots of fire.
I honestly do not know how one keeps the whole grid from
drifting
slowly up or down in frequency, but I have heard that the
long-term
frequency stability of the American power grids is superb. I
think they use
atomic standards to set the whole thing.
That few months I worked in that job was really interesting
and
amateur radio theory made it much more easy to understand this
material.
Martin WB5AGZ
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