When a generator sees a load step, there is a brief droop in terminal voltage and frequency before the generator stabilizes again. Is it possible that a voltage/frequency/speed drop due to a large load step could cause damage to the generator or circuits upstream?
With the standards imposed today (by NERC as an example), all Generators that are tied to the Grid has Protections on them to minimize the impact of system failure. All Generating Units has their own Protection. The Governor Controls and the Exciter Controls for that generator are configured to have protection. For the Exciter for instance, they are configured to have Limiters for the Under and OverVoltage. It will trip the Generator if it sees huge voltage changes for a certain period of time. The Governor Controls has Droop settings. If the Governor is reliable it will maintain the speed (synchronized to the Grid) no matter what as long as the Generator is tied to the grid. And the last line of defense is the protection System (protection System) for that Generator, they are configured to trip the Unit at a certain parameters like over speed, over voltage, etc, etc.
In our case, we have a remote Hydro Plant that is connected to a 300Km Line, and this line is always affected by lightning. If a lighting event occurs, there will be a huge voltage change on that long line, the Plant and Generator Protection sees those voltage change, and it will trip the Generator breaker to prevent damage to the system.