Traction Feeders

<...how 3 phases are distributed in traction line?...>

On overhead-electrified railways, the power line is one phase of a medium-voltage AC supply and the return is via one of the two running rails, the other being used for track-circuit signalling systems.

"Neutral sections", effectively an insulated piece of overhead wire, are arranged between overhead sections that are adjacent to each other and of different phase, so that the pantograph cannot be in contact with both phases at the same time; were it to do so then either the circuit protective device(s) of one or both feeders would operate or the pantograph would evaporate. The train effectively coasts through the neutral section before picking up power from the new phase in advance in the direction of travel.

Electrical systems in multiple unit trains are arranged so that there is no possibility of the power from one unit, which may be connected to one phase, being applied to the equipment in another unit, which may be on another phase.

For single-vehicle traction units with more than one pantograph, the neutral section is always longer than the distance between the two pantographs, so that the vehicle cannot be connected to two phases simultaneously.