That would be a major investment at every 3rd rail station on the network. It is unproven in practice, and attaining a reliability adequate for even a 3rd rail station would potentially be subject to years of development in use. It could only be justified during a project to replace life-expired 3rd rail infrastructure and would likely cost more to implement that an upgrade to 25kV OLE.
Except the costs of 25kV have been demonstrated by actual projects is astronomical.
A normally dead section of rail in the centre of a station platform doesn't require any new technologies to be developed - nor does it have to be safety grade protection because at no time would the rail be assumed to be dead.
It working reliably 90% of the time still reduces the risk of people falling onto the platform and getting a shock by 90%......
The you have been warned defence is no longer acceptable,
It's not the "you have been warned defence"
It's the "people are less likely to tresspass due to better signage, so the risks are lower" defence.
If better signage reduces FWI occurences by 20%, the value of other engineering works to reduce those injuries falls by about 20%.
especially where the cost of a proven safer method of electrification is within the limits of 'reasonable'.
If by reasonable you mean "so high that the electrification programme has been killed by them".
The losses are great in metro areas because of the very heavy currents involved in running high density services. In rural areas, the the legnth of lines becaomes the problem. Feeding a 3MW load at the end of miles of steel rails still requires track feed points quite close to each other.
Why are we feeding through steel rails?
The conductor rails would be made of aluminium with a thin steel wear surface, as is used in most third rail systems in the world, and most of the return current would be flowing through aluminium cables connected in parallel with the running rails?
High cross section low voltage cables made of aluminium are really cheap compared to the cost of anything else on the railway.
This is not the 1920s or the 1950s.
Also in what rural environment would the traction load be 3MW?
Even a Class 444 is only 2MW.....
A more likely load is about 1-1.5MW
Even two 3-car Class 377s is going to be way less than 2MW.
EDIT:
Even a 5-car Class 802 only has 2.1MW of engine output.....
All of the capital equipment and it's high cost of ownership along a moderately busy mainline would make electrification (by 3rd rail) a very bad business case. To electrify a line like Manchester to Leeds with 3rd rail would be insane: heavy trains, significant gradients, ice issues, and very remotely located unprotected ground-level conductors would be rejected outright on first application.
Who said anything about Manchester to Leeds?
Given the capital equipment costs of a railway project of the type (more like Marshlink or WEML) I am recommending are believed even by Network RAil to be drastically lower than the 25kV solution... thats a hell of a lot of cost of ownership!
Because a) as hwl says, with 3rd rail trains, little if any regenerated energy gets as far as the substation because it is either used by other trains or merely disappears into the series resistance of the track and feeders
and b) with ac, there is no need for complex converters at feed points, - any passive transformer is a bi-directional device and will accept the regen energy for returning to grid. The electronics to generate an in-phase return ac waveform (or an increased DCV) is inherent in the design of the traction control equipment fitted to all current EMU designs.
You mean "complex converters" like those currently being installed as part of the ECML PSU2 upgrade?
AC Regeneration is not nice for the grid at all, since a train is inherently a single phase load and the grid really doesn't like single phase loads.
Power electronics in the railway power distribution system are the future.