
On a 4800V system with 15Kv class gear when running a arc-flash study based on IEEE-1584-2002, the gap distance for 15Kv gear is 153mm as opposed to 102mm for 5Kv class gear, however when you run the serino of a 4800V system on 5Kv gear with 153mm gap distance the category increases 1 class in most cases why is this if the clearing time does not change and the available fault current remains the same??