Is it permissible to land wires to a spare breaker while the panel is energized (as long as the spare breaker is off)? In reading NFPA 70E, it seems like it can be done. Is a energized electrical work permit needed? Is an arc flash analysis needed?
For that matter, is an arc flash analysis always needed before working on energized equipment?
There are 3 issues here. #1, can you justify not shutting the whole panel off? Think about that as if you were in court trying to convince a judge as to why you could not shut it down. If the live work cannot be justifed, shut it down. If you think it can be justified, continue reading (And yes you need an EEWP).
Issue #2, shock hazard, if you cross the RAB with either a body part or a conductive object you are required to waer shock protection PPE rated for the voltage level you are exposed to (Which you have yet to mention), in most cases this simply means rubber gloves.
Issue #3, arc flash hazard, you either need to conduct an arc flash analysis or use the tables to select the required arc flash PPE, to use the tables you need to ensure your available fault current and clearing time of the upstream protective device falls within the limits of the tables (Notes).