Alan just a thought or two.
I would see the top visible floor/level as the "turbine floor" (of the Turbine Building where the T/G set (Turbine Generator) is located. Under that the main condenser, steam re-heaters, fed water heaters, feed water pumps and piping. Under this the "switch-gear and battery rooms. As I think about it never saw a Turbine Building with window on other than the turbine floor. But I think I would show this detail behind the lowers windows.
The "steam-generator" what power plant boilers are called are large tall rectangular boxes which are placed side-by-side. Not the horizontal tank like boilers we saw in our school building's boiler rooms. These steam-generators have eye level viewing ports to see the fires. Oil piping at the base to feed the jets for start-up, with the steam-drum at the top. The steam-generators away from the turbine building in structures that were not totally inclosed. So if I modeled be in a structure adjacent to turbine buildings under the conveyor but connected with large piping (24/36-inch scale).
The main output transformer(s) would look like the transformer used by MTH with their Schnabel car (one per T/G set.
just thoughts
Ron