🚀 go-pugleaf

In article <d3979d5f.0209101145.1a1d5a7f@posting.google.com>, Richard
Catlow <RBCatlow@aol.com> writes
>David Winter asked:
>
>> With 3rd rail systems, what is the spacing between substation (ie range of
>> one substation).
>> 
>> This will vary with system and load.
>> 
>> My question is looking at 3 min frequency, 6-car full size single deck
>> trains, with a 750v nominal supply with either medium (+/- 100v) or wide
>> tolerance (+/- 200v).
>> 
>> I know there's some well versed electrical engineering types who lurk
>> hereabouts - so some indicative figures would be helpful noting that each
>> situation requires its own assessment.
>> 
>> Also, what's the range of nominal voltages used with guarded types of side
>> contact 3rd rail systems (eg Docklands). I know that 1200v DC was used near
>> Manchester - has any system been implemented with higher DC or AC voltages
>> in a 3rd rail supply?
>> 
>Well David, there are many more variables that require assessment to
>answer your question with certainty, these include:
>
>The traction characteristics of the train(s) involved
>The stopping pattern
>Geographical and topological data including gradients, curvature,
>tunnels etc.

<snipped a bit>

Another very interesting bit of reading. Can you explain why the tunnel
would be significant please?. Is it to do with wind resistance perhaps.

Very surprised that the rail resistance is so low as you quoted, still
never actually measured a bit.....
-- 

 Tony Sayer