Yes, the military uses 400 Hz, as do almost all Aircraft bigger then a puddle jumper. Guess what, every day, at any large airport, the ground crew plug in and unplug connections to aircraft., These babies can be very large and can Arc and go to ground.
We think only about people during electrical maintenance being subject to ARC Flash. However, there are may people plugging in large equipment such as welders, and cranes and forklifts. ( I have seen 600 ampere 480 volt plugs..
One real bad accident that I heard about was a stinger accident at a rail system. These stingers consist of a metal electrode on a long pole and a long cable, They are rated at 600 to 750 VDC and are used to move rail cars in a shop by touching the electrode to a car 3rd rail shoe. They are rated at hundreds of amperes at 600 or 750 Volt DC. The person stinging a car, has to walk along the car as it moves, so the personal often loop the cable over their shoulder. In the accident the cable was wore out and parted and the person receive a severe shock
and was injured. The facility did not share the extent of injuries for the usual reasons. They asked how this accident might be prevented. The answer was in a picture on the Los Angeles Subway website of a person doing a stinger operation. In this case the person was suited up adn covered with the usual lineman's set of rubber blankets gloves and sleeve covering his entire right arm and shoulder, along with safety glasses and helmet. His entire right side was protected.