Overhead electric max power draw

[matacaster]

On several threads, the subject of the power draw of freight locos or high speed passenger locos exceeding the capacity of more than one is in a section.

Could a second wire be dropped alongside the existing catenary, but electrically insulated from it with a separate power supply to beef up the available capacity. If possible, surely this would be a relatively cheap option?

 

[jopsuk]

as far as I understand, the wire itself is not the issue- rather than the complexity of hanging parallel catenary wires, surely easier to add extra sections?

 

[NotATrainspott]

On several threads, the subject of the power draw of freight locos or high speed passenger locos exceeding the capacity of more than one is in a section.

Could a second wire be dropped alongside the existing catenary, but electrically insulated from it with a separate power supply to beef up the available capacity. If possible, surely this would be a relatively cheap option?

That's basically what an autotransformer system does. While the train sees 25kV AC, the effective power capacity is that of a 50kV system. Going beyond 25kV for train supply will incur the law of diminishing returns - e.g. needing much greater electrical clearance distances. The only 50kV systems in existence are mining railways which don't really operate as part of the wider network.

 

[dm1]

As far as I can tell, there would be no point in electrically isolating the wires. That would just cause synchronisation issues. If you can supply additional power, the wire shouldn't be the issue.

In any case multiple wires on the pantograph is a fairly regular occurrence. The overhead wire is not continuous. Sections curve upwards at either end with an overlap with the next section.

Similarly the wire is not constantly in the same position with respect to the track - it oscillates from side to side to ensure the pantograph is worn more or less evenly

 

[Bald Rick]

It’s not about the electrical capacity of the contact or catenary wire (at least not in any circumstances likely on the UK network).

It is, however, all about the capacity of the grid supply point and substations, and this comes down to two things: transformer size, and phase imbalances.

 

[aleggatta]

It’s not about the electrical capacity of the contact or catenary wire (at least not in any circumstances likely on the UK network).

It is, however, all about the capacity of the grid supply point and substations, and this comes done to two things: transformer size, and phase imbalances.

Exactly this. The Current Carrying capacity of the catenary is enough, and is actually relatively low current due to the high voltage, it's the supply grid supply and relevant transformers that is the limitation, and there is little point in uprating the transformers if the supply from the grid can't handle it.