Hi dave,is it 4000 volt or 4000 amp switch gear.I don't know if this is the correct answer but if you are thinking of drilling around live bus bars your taking a serious risk. I have worked with a fews guys that have spent time in the burn ward because someone didn't want to shut down the power, and the scars on their face and hands aren't to pretty. Anyway I've done some drilling and tapping around live parts and used cardboard and duct tape to catch shavings but the power was much less than 4000 amps, still doesn't mean it's safe, personally I think it's a trick question and the answer is do it when the power is off.
