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Author Topic: Great Western Main Line electrification - ongoing discussion  (Read 104058 times)
TonyK
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« Reply #870 on: September 22, 2019, 04:57:00 pm »

300 Amps is not an usual peak starting current for intercity type trains

7.5 MW is a lot to ask of diesel engines, especially when it is needed only for a burst to overcome inertia. There are two ways of looking at the effect of having bi-mode IEPs, though. One could say that they are a blessing, because they allow IEPs to penetrate further into the uncharted wilderness that lies outside of the M25. Or one could say that they are an excuse for not finishing the job of electrifying the GWR completely, and therefore kicking the can down the road yet again. As for blaming Network Rail - I am sure they would have been happy to finish the job, had DafT let them.
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« Reply #871 on: September 24, 2019, 06:38:34 pm »

300 Amps is not an usual peak starting current for intercity type trains

7.5 MW is a lot to ask of diesel engines, especially when it is needed only for a burst to overcome inertia. There are two ways of looking at the effect of having bi-mode IEPs, though. One could say that they are a blessing, because they allow IEPs to penetrate further into the uncharted wilderness that lies outside of the M25. Or one could say that they are an excuse for not finishing the job of electrifying the GWR completely, and therefore kicking the can down the road yet again. As for blaming Network Rail - I am sure they would have been happy to finish the job, had DafT let them.

I agree that a rolling stock based diesel will unlikely be viable to produce 7.5MW  This is the advantage of electrification via fixed equipment (OLE / third rail etc)  750V dc is typically limited to 6kA (4.5MW) the dc circuit breakers are typically set to 4 or 6kA a few places they are set to 7kA.  Rolling stock is also programmed to the max for the route even in multiple the overall will not exceed the route max.  The same is done for most ac traction a max current is set for the route, there are some issues with multiple loco's on some freight services where they the FoC has not set the current limit this cause the substation circuit breakers to trip or worse case the wire burns down.

Back to the point, electrification will always provide a quicker acceleration that diesel; the IEP's were originally intended to provide some capability to operate off wired routes, allow for diversions, operate a service when the OLE is not powered and emergency moves; like all things there has been mission creep
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