Tesla, OCP does not protect against the type of transient spikes you're talking about, because they happen far too quickly for a fuse or breaker to interrupt, and are over. You need a surge suppressor for this. Suffied to say, NEC does not require secondary OCP if primary is fed from an appropriately sized OCP. The 450.3(B) tables and secondary OCP are related more to bus taps and such.
