Wednesday, 11 October 2017

Cable Hunting

Tuesday 10th Oct

A Cable fault lineside of Winchcombe Signal Box was the subject of  today’s labours under the direction of Neil C. Two cables go under the tracks from the box and needed digging out of the ballast - one is the Toddington communication cable and one is the Cheltenham communication cable. A very time consuming and awkward job to tickle the ballast out from under numerous rails.

But after much concerted digging all was revealed

There has apparently been an intermittent fault on the Toddington line for some time so a bit of testing was now required to try and determine the location. The clever bit now follows!
From the cable end connections in the Signal Box, an electrical pulse is sent down the suspected faulty wire using a Time Domain Reflectometer (wow!). If there is a break/fault this pulse is reflected back down the wire and the instrument measures the time this takes thus giving a measure to where the fault lies. This indicated that there was a fault within 38 metres. So.....further digging ensued to try and locate the Toddington cable circa this distance:

Next stage was to bore into the cable to uncover the “offending wires” inside. This means cutting off the covering sheath, cutting through the steel armour and the plastic insulation, to eventually bare the wires in question and to carry out a short circuit test. All this led us to believe that we could remove a length of cable between 25 and 38 metres from source - this would enable the existing cable to be connected into the adjacent lineside box and a new piece of cable to be installed from this box to a new box beyond the 38 metre point. In the last picture the savaged cable is temporarily protected with a piece of plastic tubing. A freshly prepared lineside box now ready for a bit of concrete:

Neil will need a few hours of quiet concentration to reconnect cables when the railway isn’t running!
A new piece of cable is now standing by 

To protect the cables running under the tracks, concrete troughing has been installed. This will give protection from  burning coal which can  cause damage  and makes it evident where cables are 

Back at the workshop we have been restoring more lineside cabinets which will be required around Broadway to connect all the cabling that will be required there


1 comment:

  1. A very interesting day , it was relief to find that the TDR information was accurate. However it took a lot of very heavy ballast digging. Threading the concrete troughing under the existing trackwork was very heavy work- I have nothing but admiration for Neil, Keith and Carl who did most of the heavy stuff. Well done chaps.