Another problem with restoring power is that the plants themselves can only pick up load at a relatively slow rate. When the lines trip, the plant will not have anywhere to put the power they are generating and will have to shut down. Then when the dispatch center is ready to start restoring power, the plant will have to have power to run auxilliary equipment. Some plants will have small units that can be black started, and the output from these is used to provide enough power to get a larger unit online. If the plant does not have any black start capability it will need outside power for a while to get rolling. Our units are fairly small, and the loading rate is only about 2 megawatts every 5 minutes. The time between load increases is necessary to allow the boiler a chance to catch up with the higher load being placed on it. If a gas turbine (jet engine) is being used they can be loaded a bit quicker, but you still have to allow time for temperatures to equalize between load changes.

Anyway, a major factor in restoring power is finding a way to add load slowly enough that the equipment can keep up. It can be a game of trial and error, since it is very difficult to know exactly how much load is waiting when you close in a feeder.

Also, on the electrical grid, frequency is the controlling factor. When the frequency dips, the generators will automatically pick up load to try to correct it, and when the frequency rises, the generators will reduce load to correct it. If the frequency is too low the units will trip on underspeed and have to be restarted.

Boy oh boy, sorry folks, I could go on for hours here. [Linked Image]

Anyway, I hope that might help a bit.