Work Space for Unit Substation

[dahualin]

I am designing a unit substation for one project. The unit substation includes one primary equipment of Medium Voltage Metal-Enclosed Switches (13.2KV), one dry-type transformer (2500KVA), and three sections of low-voltage distribution switchboard. They are rear accessible switchboard. What is the minimum work space around the unit substation? I have checked NEC Table 110.34(A) Minimum Depth of Clear working space at electrical equipment that shows 6 ft in condition I for 25,001V~75KV. Does it mean we need put 6 ft space around the unit substation? Thanks.

BTW, how many hours fire rating for the electrical room required? Thanks.

 

[kingpb]

13.2kV I assume is the line-line voltage, which means the line-gnd voltage is 7.62kV, which is either 4, 5, or 6 ft depending on Condtion 1, 2, or 3 respectively.

I would imagine that since you only work on the gear from front or rear, that the sides do not need to be 6'. But without more info can't make that call.

As far as fire rating, I would assume 2-hr, but whoever does the building code review would best be the one to determine.