Why Double/triple catenary wires at Crewe station?

[PSi]

At a Finnish rail related site "vaunut.org" there is a photo taken from Crewe station platform about the catenary wires of the station. It appears that there are three parallel catenary and contact wires running on common cantilever arm and registration arm:

    http://vaunut.org/kuva/141457

There seems to be two parallel wires at least on platform 5:

    https://upload.wikimedia.org/wikipedia/commons/c/ca/Crewe_railway_station_MMB_02_350259.jpg

Why two/three parallel wires? Why all are supproted on common supports so that they may not be individually tensioned?

 

I have not found any technical reason or explanation for this. Where I could find a reason behind this?

 

To my understanding, the vertical control of the contact wire is by cantilever arm or swivel arm supporting the catenary, and contact wire being supported from catenary with droppers. I trust that registration arms are only used to guide the contact wire horisontally. All reference I've seen so far suggests that parallel wires need their own cantilever arm to individually  compensate the lengthwise movement due to expansion and tension. What I've seen is, that crossover wires have separate cantiliver arms (swing arms) and registration arms attached to it to make them mecanically independent, and to allow individual tensioning and lengthwise movement. The exception only being the anchoring cables attached to cantilever / swivel arm at the middle of long catenary wire.

Do you know of any freely available matrial on the Internet that I could see about having parallel wires in same cantilever and/or registration arm in UK?

 

The stuff I've found:

 

"Network Rail: A Guide to Overhead Electrification", February 2015 Rev 10 by Alan Baxter,

https://www.bathnes.gov.uk/sites/default/files/sitedocuments/Planning-and-Building-Control/Planning/nr_a_guide_to_overhead_electrification.pdf

 

and

 

"Overhead line electrification for railways", 4th edition 2016 by Garry Keenor,
https://www.railwaysarchive.co.uk/ocs4rail/download/Overhead-Line-Electrification-for-Railways-4th-edition.pdf

 

have no mention about having multiple catenary wires supported by common cantilever or multiple contact wires guided with common registration arm. A bit of googling (Google map googling) reveals that it appears that Crewe has "double wires" or "parallel wires" at least on tracks at Platform 5 and platform 6:

https://goo.gl/maps/aevtpnj2RnT46ASXA

but not at platform 11. The catenary on above photo is supported with single cantilever arm and the registration arm is connected to one contact wire and the parallel contact wires are connected to each other with some sort of links. The parallel catenary and contact wires cannot independently move lengthwise, so they must act as "strands of a common cable" or something. I still cannot find description telling why 25 kV line would needs doubled or tripled catenary and contact wires, and how the three wires are individually tensioned...

 

E-mail to nationalrail.co.uk  and avantiwestcoast.co.uk (on June 2021) has not come up with any help yet.

 

pekka

Edited December 13, 2021 by PSi
Typos, typos, typos...

[jim.snowdon]

First, given the complexities at each end of Crewe station, particularly the north junction, the OLE is probably what is termed 'fixed termination' equipment, where both ends of each catenary / contact wire run are anchored directly to a structure, rather than to movable balance weights. The tension is set by pre-loading the wires to a required tension, and then varies according to temperature - in hot weather the spans sag a bit more and vice versa in the cold. A feature of this is that the wires do not move along the track with temperature, unlike auto-tensioned OLE.

 

Second, the use of multiple parallel wires is almost certainly to do with the lack of suitable anchor points within the length of the train shed, from which much of the OLE is suspended. It becomes simpler to just run converging wire runs together until they diverge again at the other end of the station. It can also make it easier to cope with crossing wire runs in the junctions, as the wires can be 'crossed' using a flat knuckle joint instead of actually running one wire across the other. This technique was normal practice with the 1500V DC wiring installed for the Liverpool Street/Fenchurch Street - Shenfield electrification in the late 1940s and is clearly evident in photographs of the junction work at Stratford before the recent (c.2012) renewals.

 

 

[PSi]

Thanks — Jim!

 

If this is the case, I would have thought that the two extra "full feature" sets of contact wire and catenary wire were joined and be replaced with a single cable, supported with extra cantilever arms and be anchored at next possible location, and not being used as double or triple contact and catenary system.

 

As the system is not tensioned with weights or springs, braking of a single contact or catenary wire will probably not cause sudden oscillating movement of the combined system.

 

I wonder how the lower voltage (1500V etc) double contact wire systems are terminated: Are the contact wires just considered as "two strands of a cable"...

 

Thankyou for quick and informative reply!