The limitations on how far a substation can provide power is defined by how much current can be consumed and how much voltage drop is tolerable.
Voltage drop is simply current times resistance for DC wiring.
A simple rule of thumb is that the resistance of 1 foot of 1 cmil wire (i.e. a round wire with a diameter of 0.001", which is 1 mil) is 10.6 ohms, thus 1000' feet of 1000Mcm cable will have a resistance of 0.0106 ohms.
The resistance of rail is about the same as a copper conductor with an area of 10Mcm per pound per yard, a pair of 90 lb rails is equivalent to a 1,800Mcm copper cable.
http://cs.trains.com
Jay Burkgart Wrote:
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> If the Milwaukee Road had been successful in
> electrifying the Gap, where would the substations
> have been located?