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lfcman24 t1_j5l4614 wrote

Reply to comment by pargofan in Nearly 220 million people in Pakistan without power after countrywide outage | CNN Business by calbert1735

Probably not enough fuel in generators. The grid is usually designed to sustain loss of few generators but if the demand power vs supplied power comes dangerously close even worst if the demand power is higher than supply, it can cause voltage to dip which causes generators to run at a higher speed and hence can trip those and results in a cascading effect where the demand cannot be met now by remaining ones and one by one all generators trip.

Coal Generators can take a day to two during warm start , gas ones are quick so depends what’s in their bucket. Power restoration after a grid failure can take a day to a week to complete restoration.

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Drak_is_Right t1_j5pfd5o wrote

It also takes time to sync each additional generator with the previous ones on the grid. There is a very fine window on the frequency. Just a tiny dip and everything goes down. Or explodes and catches fire.

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lfcman24 t1_j5pgtv3 wrote

Syncing is usually not that hard. The problem is that you create tiny islands when restoring after blackout and count how much reserve you have if your largest contingency/generator trips in this case. Worst case if you pick too much load after power restoration and suddenly the largest generator trips, you are back to zero. Therefore, companies design their power restoration as small pockets, helps bring all generators online and also helps supporting different island. Synchronizing islands is a bitch but with moderns AVR and frequency regulators they are pretty doable.

Load restoration is a like a total gamble because it’s all done theoretically but rarely any engineers have seen it happen in reality.

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