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