alt Hacker NewsI get that. I'm pretty skeptical that 120 KW going through the last panel doesn't cause damage, and in the "multiple miles chained together" (to quote op) many MW going through the panel at the end of the chain doesn't run into some sort of issue in the real world. Even small percentage losses turn into a lot of heat or other issues at that scale.
If it doesn't why not just make the whole 100 mile stretch of canals discussed a single very long daisy chain of panels, and still address the concern of the OP in terms of extra material for conductors?
It won't! That's the amazing thing about electricity.
While having 12kV going through panels is not safe for many reasons, having 300V at 10-20A is completely normal.
12kV is impractical because these voltages can jump quite far, and you need a lot of insulation for them to be safe.