>>1702801>I would argue increasing substation density improves redundancy which is good for infrastructure grids, especially in cities.It doesn't.
25 kVAC lines are simple as fuck. You have 50 kVAC wire going somewhere near tracks, and you have autotransformers every once in a while to turn 50 kVAC into 25 kVAC.
DC substations are more complex, as you have rectifiers there.
As for redundancy, nothing stops you from having 110 kV to 25 kV substations every kilometer, price would be the same as main piece there is transformer.
> Naturally that argument is why 750VDC gets used in metropolitan transit. More like insulation gaps. 750 VDC doesn't need thick insulation. I think even house wiring would handle 750VDC if you try hard enough. 25 kVAC - you need giant ass separating gaps from train roof, from tunnel - this means you need bigger tunnels, and bigger tunnels are expensive. (which is why you don't get much subways with overhead powerline). Or imagine a tram which has 25 kVAC instead of 550VDC, with wire hanging on half meter ceramic insulators and panthograph is big.
Another thing is that AC trains are hard. DC is easy. Resistors - yeah. VFD? yes. Meanwhile on AC, you need transformer. If you want regen, you'd need some weird schematics, etc. (well... in DC substation does this)
>3kVDC vs 25kVAC at this point is a business decision, but 1.5kV seems like the paste eater's choice.Nah. 16.7 Hz is the real shit, because you'd need even more complex substations than on DC, as 16,7 isn't 50.
