A large solar storm is unlikely to damage many transformers. Transformers have low impedance, yet solar storms have the biggest impact on high impedance systems (like copper telephone cables, especially when 'on hook').
The only time a power network is high impedance is when it isn't connected (ie. when part of the power network is switched off). Trivial operational changes could be made to ensure that offline parts of a power network are grounded during a solar storm.
Reserve transformers might be a good plan for other reasons - eg. fast recovery after a war on US soil - transformers are usually early targets in war, and hard to defend.
A large solar storm is unlikely to damage many transformers. Transformers have low impedance, yet solar storms have the biggest impact on high impedance systems (like copper telephone cables, especially when 'on hook').
The only time a power network is high impedance is when it isn't connected (ie. when part of the power network is switched off). Trivial operational changes could be made to ensure that offline parts of a power network are grounded during a solar storm.
Reserve transformers might be a good plan for other reasons - eg. fast recovery after a war on US soil - transformers are usually early targets in war, and hard to defend.