Eli5 how could an electromagnetic impulse, say from the sun for example, disable a whole power grid?
In: Physics
Lets say you have a high voltage transmission line going between a power station and a city. These can be hundreds and even thousands of miles long. So if you get a powerful electromagnetic wave hitting it then it will act as an antenna and the wave will create a current in the line. Since the line is so long you can get a huge current in it from this electromagnetic wave and more then likely some part of the line will not handle the current and melt. The power grid is made up of these transmission lines all connected together.
But even if these transmission lines will fail, hopefully it will just blow all the fuses, it will be an easy fix that would take no more then a few days for linesmen to go around fixing all the issues. The real problem is with the more sensitive equipment like switches, transformers and generators. In addition to being much more complex and therefore much harder to fix they also tend to be enclosed in an oil bath to prevent short circuits in the extremely high voltages they operate in and also to cool the equipment better then air. So not only do you need to unwind a huge coil to get to the part of the wire that failed and then wind the coil again but most of the coil will not be there any more as the oil have burned it away. If you get any of these high current events in just a fraction of the transformers it will cause huge issues for the grid as you can not transfer power from the power stations to the cities any more. And it is not like you can just order a new transformer station to be delivered the next month because there are very few factories making them in the world as the demand for new power grids is relatively low.
The current plan for dealing with such an event is to be able to detect it early using space probes that have been installed between the Sun and Earth. When we have detected a wave of charged particles from the Sun strong enough to damage our power grids we will shut it all down. Turn off all the power stations and disconnect all the switches. It will probably require linesmen going out and manually disconnect huge disconnected or even cutting some of the lines intentionally. This means that when the electromagnetic pulse arrives we will not have one huge grid but only small pieces of lose wires around and these will not build up as much current as the longer lines would. Most importantly sensitive equipment like power stations and transformers will not be connected to the grid.
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