What kind of cable can be used to power a mobile electric machine running of 6 kV AC?
EDITED - don't bother trying to say it has a diesel engine like I did because it comes in two versions.
This version has an engine: -



And presumably it cannot be powered from a trailing cable.

If it helps save my reputation, I've worked down coal mines with really powerful electric machinery operating at 3,300V 50Hz and these were +1MW machines that ran up and down a "longwall" coal face shearing coal off onto a conveyor belt. The cables, from memory were about 4 inches diameter and as tough as old boots.

The trouble with the Hitachi is that if it over-extends itself it's going to unplug itself from the static generator and it's going to be a real b**ch to plug it back in!