How on earth does the power supply to an entire Country fail?
In: Engineering
One possible scenario is that one or couple of generators could get disconnected from the system and the remaining generators are unable to sustain the load, they start slowing down, just like trying to get up the very steep hill with a bike. Because many devices and the generators themselves were not designed to to work at lower frequencies than nominal, at certain point the generators protections kick in and start disconnecting the generators from the grid. This lowers the frequency even further and other generators start disconnecting as well. So on the system comes to a complete halt. Nowadays I’ve not heard of such cases, because most of the time there is a sufficient reserve in the system to back up any generator that might unexpectedly fail. And if that is not enough, protections will start disconnecting users to reduce the load before they disconnect the generators.
Another reason for a blackout is related to the lines and orher type of current carrying components. The electrical system most of the time is connected in loops, so that if one line fails, the city or strategic point could get the energy from another line. The issue is that sometimes, due to economic, maintenance or other reasons, the loads and generators might distribute in such a way, that some of lines might get near to their capacities. And bam, a short circuit happens on one of the lines, because a tree fell on it and it gets disconnected. Then the other lines take on the load, but they don’t have sufficient capacity to carry so much power and their protections kick in, and disconnect them due to overload. Then the cascading begins and the system might get seperated into multiple smaller systems with uneven load-generation balances and they start collapsing on their own, just like in the previous case.
But today, not many blackouts happen, maybe in the third world countries, because people have gathered huge amounts of knowledge in this field and current protections are very well configured, there are plenty of redundancies, generation reserves and online contingency analisies being made to avoid such situations. In most cases multiple things need to fail at once or somekind of catastrophy to happen to take out the whole system.
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