But then I said "well what happens if my Department of Energy gets taken over? Would I loose all my power line buildings? Would the entire nation loose power?" So I came up with a solution ...
The "Department of Energy" national wonder would make "Transformer Stations". These do not provide any "power" like the power lines do. However it would allow power to be distributed to the entire nation. If the "Department of Energy" was taken over all the "Transformer Stations" would disappear and all cities would loose access to the "national megawatts".
However the "power lines" would not be forgotten but are now a required building for all power planets (as stated before). And would not be built by the "Department of Energy" national wonder but have to be produced by hand. It (unlike the transformer stations or power plants) would provide "power" (not megawatts).
Thus a city could still use their "local megawatts" if they had enough megawatts from their cities power plant(s). In short ...
Department of Energy = Gives free "Transformer Stations" to every city.
Transformer Stations = Gives access to "National Megawatts" at 1/3 the amount. Can only be built by "Department of Energy" national wonder.
Power Lines = Provides "Power" to each individual city. Is required to build power plants.
Power Plants = Provides both "local megawatts" and "national megawatts". Requires "power lines" to be built.
Local Megawatts = Provides megawatts to an individual city. Any extra megawatts gets added to "national megawatts"
National Megawatts = The extra megawatts produced by "power plants". Can only be distributed by "transformer stations" when the "Department of Energy" national wonder is built. The amount sent to each city is 1/3 the amount put in.
I hope I made everything clear. And no I do not know the math for all that.