(10-04-2018, 03:40 PM)danbrotherston Wrote: It's interesting that this is validated through simulation only. It seems like it should be easy to test in a practical situation--simply setup the specific required scenarios, and measure voltage drop, heat load at substations, vehicle performance, etc.
The simulation is part of the design requirements, i.e. the design must be validated by simulation before any purchasing or construction begins. A highly sensible requirement!
(10-04-2018, 03:40 PM)danbrotherston Wrote: I would be curious as to how much margin there is. There was an article I read a while back whose author (who claimed to have electrical engineering credentials) was claiming that traction power systems on new LRT systems like ours were massively over provisioned leading to more wires (double wires) and resultingly, heavier more expensive cat poles.
This seems quite believable to a non-expert such as myself given that TTC is running similar vehicles with lower headways (but only single trains I believe) on a much lower gauge system, which I would expect would have lower capacity. Now I'm not an electrical engineer so I cannot know for sure, but it does seem curious how much more substantial our system is than TTC streetcar wires.
Our system and the TTC's are quite different in this regard. They use a single wire system, with buried underground feeders that connect to the overheard every few poles or so to prop up the voltage. Our system is dual wire with a contact wire suspended from a messenger wire. The benefits of this are two-fold:
a) The messenger wire works like the cables in a suspension bridge to keep the contact wire level and ensure good electrical connection with the pantograph at all speeds.
b) The messenger wire is sized larger than the contact wire and connected to it with regularly spaced 'droppers', so that together the two can carry the full load current for the scenarios described above without expensive underground feeders.
I think our dual wire system was a great compromise. With single wire and underground feeders like the TCC, our system would have cost over a billion and probably never would have been approved/passed/built!
...K