The target analysis methodology US Special Ops forces use is unclassified, Weapons Man notes:
It is described by the acronym CARVER. That stands for Criticality, Accessibility, Recuperability, Vulnerability, Effect, and Recognizability. A brief definition of Criticality might be: “how critical is the targeted node to the target system, or to the enemy’s war-making capability?”
CARVER works as well when planning to protect or defend a target. For instance, it systematizes developing CT countermeasures or securing a target against exploitation by reconnaissance, surveillance, or attack. The primary product of CARVER is a thorough understanding of the target, target system or target complex by the assigned team, but they also produce a target folder. (In the real world, they’re usually updating a preexisting target folder, which might be a half-century old). One of the documents they produce, for each target, is a CARVER matrix which can be unweighted, but in the real world is usually drafted with weighted values. The weights depend on overall mission objectives and priorities. (For example, CARVER values are weighted differently for a clandestine attack in a time of nominal peace, than they are for an overt attack in time of war). This example of a simple, unweighted CARVER Matrix is from Appendix B to FM 34-36.
Herschel Smith describes the terrorist attack that America cannot absorb:
The most vulnerable structure, system or component for large scale coal plants is the main step up transformer — that component that handles electricity at 230 or 500 kV. They are one-of-a-kind components, and no two are exactly alike. They are so huge and so heavy that they must be transported to the site via special designed rail cars intended only for them, and only about three of these exist in the U.S.
They are no longer fabricated in the U.S., much the same as other large scale steel fabrication. Its manufacture has primarily gone overseas. These step up transformers must be ordered years in advance of their installation. Some utilities are part of a consortium to keep one of these transformers available for multiple coal units, hoping that more will not be needed at any one time. In industrial engineering terms, the warehouse min-max for these components is a fine line.
On any given day with the right timing, several well trained, dedicated, well armed fighters would be able to force their way on to utility property, fire missiles or lay explosives at the transformer, destroy it, and perhaps even go to the next given the security for coal plants. Next in line along the transmission system are other important transformers, not as important as the main step up transformers, but still important, that would also be vulnerable to attack. With the transmission system in chaos and completely isolated due to protective relaying, and with the coal units that supply the majority of the electricity to the nation incapable of providing that power for years due to the wait for step up transformers, whole cites, heavy industry, and homes and businesses would be left in the dark for a protracted period of time, all over the nation.
As bad as the recent Metcalf, California attack was, it could have been worse. The West Point Combating Terrorism Center found that an attack on well-chosen nodes could take down one of the three regional grids powering the US.