If a large AC synchronous generator, like one from a hydro dam, were to receive overdemand from the grid, would it start losing frequency or losing voltage?
I know they have several safeguards to keep this from happening, but if these safe guards were not in place, what would be expected to happen?
Edit: Supposing there is only this generator in the whole grid.
Best Answer
It depends on whether the weak link is the generator itself or the prime mover.
If the construction of the generator limits its power output — the resistance of the wire, the strength of the magnetic field, etc. — then the voltage will sag, even while the torque on the shaft remains within the capability of the prime mover, so the frequency will not change appreciably.
On the other hand, if the prime mover is undersized with respect to the torque that the generator can produce, then it will slow down, and both the frequency and the voltage will drop.