I have worked on some 5,000 hp at 4,160V, and they have to notify the utility company when they start them.
About 500 amperes or so, and so the cables are not excessive.
As you go up in horsepower, the cables would get rather large at 4,160, and so the higher voltages would be worth the trouble for the extra insulation.
I use 5kv above 200 hp. I have not had to go above 5kv for the largest motor, which was 5,000 hp.
The local refinery has blower motor, I think rated 20,000 hp and 40,000 hp. I have seen then from a distance. Big as a house.
The big Allis Chalmers motor above is a wound rotor induction motor.
I went back and checked, and the voltage is 6,250 v, 750 hp, 115 rpm.
I think when they were installed in 1915, the local power system was probably not very stiff, and thus the wound rotor to minimize the starting surge.
I recall the incoming switchgear operating at 12.5 kv, so I guess they moderized the power system, and installed step-down transformers.
The Allis Chalmers motors are a beauty to watch run.
Runs as good as it did when installed in 1915.
The three brushes are for the wound rotor.
You can see that the base is designed to allow the stator to slide over off the rotor.