The line ended up in a terrible mess this evening following the signalling systems failure in the Plaistow area. At Victoria, the driver said that he taken over 1 hour and 15 minutes to travel eastbound from Earls Court and was advising passengers to use an alternative route.
I think that trains were reversing at Tower Hill, Aldgate East and Whitechapel.
I was curious about how a 'signalling systems failure' could happen on a line with conventional signalling?
Last Edit: Mar 30, 2018 9:53:00 GMT by superteacher: Title amended for clarity
The failure was a loss of the signal main, this is probably the most drastic type of failure we can experience as all signals on the ground will show no aspect and so they all need to be treated as showing at danger. All track circuits will also 'drop' which show signal sections as being occupied regardless of a train being present or not.
'lost' taught me the meaning of failing to push those buttons at regular intervals!
Correct with the signal main failure aka AC Main failure this is the main 600v feed for all signalling supplies.
It was actually lost between Barking and Plaistow to begin with then after the feeding arrangements was changed it was narrowed down to East Ham and Plaistow.
The actual fault was a defective cable around the Upton Park area but as Barking cabin controls everything west of Dagenham East to Bromley By Bow they actually lost control of everything in those areas for a short while then gradually regained control except for Plaistow / West Ham and Bromley By Bow. After some more isolations were carried out and again changing the feeding arrangements all signalling was back up and running. Unfortunately due to the tests involved it’s abit of trial and error until the piece of cable was found.
In the rest of the signalling world with which I am familiar, that universal force of gravity is employed acting on a dumb counterweight. Power may fail, springs might break, but the Earth - which we geologists say - continues to suck! Attraction is eternal.
Modern systems usually have a UPS (Uninterruptible Power Supply) to maintain the supply if there's a power loss. That wouldn't have been practical back when the District was signalled though (1950s?)
Even in the 1950s, battery stacks were common in railroad signaling systems. More likely that some bright-eyes thought the electric supply was reliable enough (ahem, cough) or they didn't like the cost of enough batteries and maintenance. Or... did they use AC track circuits at the mains frequency?
Come to think of it, none of the books I have about UK signalling practice, not that I have many, mention backup power. is the District line signalling based on AC or DC circuits? (Which sends me at various web sites to find out.)
Post by principlesdesigner on Apr 3, 2018 3:50:07 GMT
The District line originally used AC track circuits, and in some areas still does, the frequency of these tracks was 33 1/3Hz. The signal relays, trainstop valves, points valves & detection etc. are also AC.