That's a very dangerous situation if the components that it powers have any signal wires connected to components powered by other AC circuits...............................
(The 75 amp transformer is of course wired as a completely separate electrical system with its own 1 inch by 8 ft copper ground rod and 400 lbs of grounding mix.) The noise floor is nil.
With a nearby lightning strike, there could be several thousand volts difference in potential between it's components and the other circuits components.
If a large transformer is wired as a Separately Derived System with it's own (isolated) ground rods, you should not have any signal or data wires connected to other AC systems.