I'm starting a new series of maps to show the normal feeding arrangements of Network Rail controlled electrified lines at the present day to be best of my knowledge. I started this project a long time ago and began with the general London area with the intent to go outwards from the many directions this map fringes. Due to how dense the lines are south of London, the map is heavily biased in that axis because I wanted to make sure the fringes with future Southern maps were clear for reading between two maps.
The general idea is to colour lines by which grid connection feeds them. For AC lines this is fairly clear as boundaries must occur at neutral sections. For DC lines, the boundaries refer to normally open points in the HV AC traction power network. The intention is to suggest the architectural similarities between LV DC and 25kV AC systems. Effectively, the overhead line acts akin to the HV AC traction power network while the rectification substation is onboard the train rather than a track-side installation like on a DC line.
Here's a preview to show what I mean.
There is a complication, however, in the fact that only one grid supply can be carried by the overhead line at any one point, while on a DC railway, multiple supplies can be housed in track-side ducting. Though interestingly, most of the time on the Southern Region this is not done and lines have just one feeder route against them. On the London map, grey is used for a line which is 750V DC but no HV AC feeders run along it, and thinner lines show the approximate or logical route of other grid connections.
Going forward, smaller DC railways do not use a traction power network and connect directly to the local grid at each feeder station. In those cases and on future maps, black is be used to signify those DC lines.
The other important difference between this first London map and the future ones is that here I have not drawn unelectrified lines mainly for clarity. While on future maps these will be in grey as long as they are in some kind of passenger use. Also on other maps I will attempt to show electrical transmission and sub-transmission infrastructure (powerlines and substations at 132kV, 275kV and 400kV). This would seriously clutter an already very dense London map, and furthermore OpenInfraMap coverage of (especially 132kV) in London is quite limited. A map showing grid infrastructure in London and simplified railway lines may be something I attempt at some point.
I have been slowly refining any known errors since I first "finished" the map last summer. The only major unknowns are around HS1. I expect there to be more ATS substations visible in this map's area especially in Kent. But info on HS1 is non-existent. I was even able to find decent records on what will be the setup for HS2 phase 1 currently under construction.
A "tee-d" DC substation refers to one where the transformer/rectifier equipment is simply "branched" from the AC line and the substation has no AC switchboard, just a circuit breaker. A normal substation has at least a basic AC switchboard where 2 or more feeders are terminated. This means a normal substation has at least one layer of redundancy if a cable fails.
This time, I'm going to try and use an online pdf hosting website to upload the map (https://pdflink.to/3ee6e1d0/)
If not, just in case here's a flickr link to a rather over compressed version (still legible) (https://flic.kr/p/2rh7yW3)
