That is nothing. We had some new automatic welding machines put in last year. Each machine has a 4, 400A power supplies. When one of our 2nd shift maintenance guys wired them up they mis-wired one of the twist lock plugs. We are on 480v, 3ph. They landed one of the phases to ground. Power supplies were isolated on rubber feet. It ran for MONTHS, like nothing happened... Until a maintenance guy touched both the chassis and the frame work supporting it... You guessed it, 277v to ground in one hand and out the other. Luckily all he had was burns on each hand. I believe it has 50A fuses.
We carry NCVD in our pockets daily for all kinds of troubleshooting. I personally like the Fluke. The Greenlee I had was flaky.