How Does an Electric Generator Match the Grid Frequency?

Thanks again - nicely put and... I get it!

Is it a problem if it is out of sync when you flick the on switch?

(And if so... how do you get it in sync before you pull the on switch?)

Synchronization can be done with lights that verify same phase rotation and voltage at the time the generator is connected. An instrument called a "synchroscope" does the same with even greater accuracy.

Well I am assuming you know how AC sweeps between positive and negative polarity. If you flick the switch and say the generator is close to 180 degrees out of phase with the grid, it will be like a dead short at twice the voltage. Since the grid is, by comparison to the generator, an infinite force, the generator will most likely be damaged. Sometimes rather violently. I have heard stories of massive V16 diesel sets being ripped off their foundations. Never seen it myself though.

Absolutely. Aboard ship, bringing up one generator, paralleling it with the running generator by using either the older 3 light system or a syncroscope to insure they are in phase when you throw the breaker is very important. Just a few degrees off can produce some noticeable, even violent, bangs as they lock together. Watched a First Engineer miss-time it once and held my breath hoping nothing was going to give and we wouldn't have a blackout. Done right and there's barely a whisper. Done wrong and there can be hell to pay.

The grid is seen as an infinite force.

It will lock the generator's stator frequency to its own frequency , say 50 hz, ie 3000 pm.

Depending on the capability of the prime mover , the sync. machine will be a motor or a generator. This depends on another factor called torque angle. there is an excellent post in this forum describing it. I do not have the link to it . Searching the forums will help.

Theoretically: Generator Frequency (f) = Number of revolutions per minute of the engine (N) * Number of magnetic poles (P) / 120
Practically the thing which control the frequency called the speed governor.

Some more reading:

http://en.wikipedia.org/wiki/Synchronization_(alternating_current)

This may be of interest to more experienced members of CR4.

Live feedback. The UK network frequency.

It's quite interesting to watch when a television program is due a commercial break. The kettles go on and the grid slows slightly. At this point pumped storage stations are ready and waiting for the load to rise.

Some of the plants I worked on the PLC sent a signal to the grid control to ensure there was enough "spinning reserve on line."

We caused a few problems when one plant went off line due to a fault. 25MW of load on the grid suddenly vanished.