We did have that once where an electrician was drilling into the main cabinet with an 3 x100A 3 phase supply which was live and the shavings shorted out all 3 phases and blew all 3 main fuses, the utility was not impressed with that one.
I've had to drill into live switchgear cabinets before, but ALWAYS take proper precautions like adding a proper rated voltage blanket / line blanket to cover exposed bussing, wearing proper PPE because no one wants to live through an arc flash without it, and when drilling steel cabinets, I put a rare earth magnet where I'm drilling to catch the majority of shavings and to catch the metal "plug" before it falls anywhere.
I've seen my fair share of sketchy hot work and know people who have lived through arc flashes... its not something I EVER take lightly and take every precaution I can.
I once had to retorque and repair damaged line side bussing on a switchgear and the customer told me there was no way they could loose power and told me I had to do the work live. I knew that a loss of power wouldn't result in ANY life safety conditions and I knew that running power through the bus in the state it was in would present significant life safety hazards so I threw the main off, locked out the cabinet and called the utility company for immediate emergency disconnect.
Had it repaired in an hour and had the power restored by the utility shortly after.
There are very few circumstances where circuits, equipment or live switchgear need to be worked on live. Any properly licensed professional should know this and should be properly trained and provided ALL the proper PPE for those few circumstances where hot work may be necessary.
Just my two cents.
