Water and electrified railways ?? - Page 1
Forum section: electronics / general

author: MathWizard
author_rank: Super Contributor
timestamp: September 29, 2023, 06:37:39 pm
content: I was just looking at some of the flooding in New York, and it's common to see the subways flood, so what happens to all the electrified tracks ? What about when it rains and just little puddles are around the tracks ? I know pure water is a bad conductor, but what about dirty muddy water ? What about in winter when they might use road salt, some of that must get on or around the tracks sometimes too.

author: ataradov
author_rank: Super Contributor
timestamp: September 29, 2023, 06:53:32 pm
content: The current is carried between the rails and the side rail, which is elevated and covered on the top, so it remains relatively dry and free of piled up snow. Minor amount of rain would not cause an issue.If the power rail gets in a snow pile due to heavy snow, they will clean it first. If it gets submerged entirely under water, that segment is disabled. The rails would be submerged first before a short could occur, so it would be unsafe to run the trains anyway until the water goes down.

author: coppice
author_rank: Super Contributor
timestamp: September 29, 2023, 07:05:42 pm
content: Third rail electric trains are quite troublesome in bad weather. That's why new metro systems accept the extra height needed for a compact power pickup system above the train through the underground sections, so the sections exposed to the elements can provide better service. If you look at most underground systems with a third rail, there is a trench down the middle of the track. When there is water seepage those trenches fill, and pumps clear them. In modern metros, with overhead power, they don't usually have that trench, and I've seen them operating through problems with their rails in water.

author: TimFox
author_rank: Super Contributor
timestamp: September 29, 2023, 07:21:24 pm
content: Another problem for rail and subways is salt water getting into the traction motors during bad weather.In 1979, Chicago had an unexpectedly ferocious snowstorm (resulting in 74 cm depth of snow on the ground) that closed down most everything, and resulted in the electoral defeat of the incumbent mayor.Total removal of the snow took 59 days.A specific problem was the surface lines on the CTA 'L', where the newer lines ran down the median of expressways (Dan Ryan on the south side and Kennedy on the north side).Plowing the highways deposited salty snow on the 'L' tracks, and the existing rolling stock used self-ventilated electric motors where the fans sucked saltwater into the motor.Despite hiring all of the rewinding capability in the city, these newer lines had to shut down.On the older elevated lines, such as the "Loop" around downtown, and the Englewood/Jackson Park lines, the snow fell through the gaps between ties and caused less trouble.Later CTA rolling stock employed ventilation input from the roof because of that history.I don't remember any substantial problems with the third rail itself during that crisis, except for icing.

author: MathWizard
author_rank: Super Contributor
timestamp: September 30, 2023, 07:03:08 am
content: Ok thanks, I'll have to read something on it, I'm just looking around on youtube at some of the subway clips/documentaries. I wish someone gave a video tour of their power systems, I'm just trying to imagine what all the giant circuit breakers and whatever all else, they have now, and over the years.I should look up some industrial EE video's, like the power systems at an Aluminum plant, etc.

author: tom66
author_rank: Super Contributor
timestamp: September 30, 2023, 01:17:15 pm
content: In serious flooding, there are other problems, like train detectors (track circuits) not working correctly. I would guess if there is a lot of flood water, the train operator turns the power off, or a ground fault detection system trips power off for each section.

author: TimFox
author_rank: Super Contributor
timestamp: September 30, 2023, 01:30:35 pm
content: Even if the railroad is not electrified, the serious flooding mentioned above will cause "block occupation" detectors (continuity from left to right rail) to short out and the signal system will not function correctly.

author: nctnico
author_rank: Super Contributor
timestamp: September 30, 2023, 01:31:19 pm
content: I would assume there is also some kind of early warning system in place (for example: based on drainage exceeding capacity) to at least make the trains stop at a station so the people can get out safely.