The solar storm of 1859 had a large effect on telegraph lines, which ran for long distances but carried tiny amounts of power. The amount of energy imparted to a line is proportional to the length of the line.
An electromagnetic event that dumps 0.1 watts/meter on a ten kilometer long telegraph line line will put a thousand watts of power into it. This is going to have a dramatic effect on a line that normally just carries a couple of watts of power to run a telegraph clicker. The same event may not even be noticed on a modern power line that carries megawatts.