I have been interested in finding out more about this topic but I can't seem to find any articles/periodicals that don't assume you to already have 20 years experience with under frequency load shedding in transmission engineering. My questions are: 1.) How is it that you determine the amount of load that has to be dropped? I'm assuming it has something to do with the power angle coming from the generators, but I'm not sure if that's correct. 2.) What frequency is considered "too low"? In other words: What frequency separates the steps from one another? 3.) In the case of an under frequency event; how long would it take for the generators to "get back to speed" after the appropriate amount of load has been dropped? 4.) Is there a point where, no matter how much load is dropped, the generators cannot re-right themselves and they have to be re-started? What would cause such an circumstance? Thank you, -Tyler.