Railway signalling earth faults

[JohnE1959]

Does anyone know what process network follow when trying to trace earth faults on the Signalling Equipment?

 

[John Webb]

I assume that you are aware that most signalling equipment, particularly colour-light signals and the like, run from a 110v AC supply neither pole of which is earthed? (Unlike the 110v used on construction sites which is centre-tapped to earth to minimise any shock hazard.)

Some locations are equipped with circuitry which automatically detects an earth fault and on which side and can immediately raise an alert. Otherwise it's the usual means of finding a faulty circuit. I haven't worked for NR, so I don't know their exact process, but I would expect it would spell out the process in detail to minimise the possibility of causing a 'wrong side' indication during the work - Clapham Junction 1988 is always a reminder of what can go wrong.

 

[CW2]

Mildly off-topic: many years ago I was a booking boy at Willesden PSB. One long night shift the signaller received a call that there was an Earth Fault affecting the signalling by a set of trap points by Willesden Brent Sidings, but "it will be self rectified within the hour." What had actually happened was that the 08 shunter had split some points and landed on Mother Earth (hence the phrase "Earth Fault") but that the local crew were getting it back on the rails without the knowledge or intervention of any management! So the phrase "bad earth fault" always means "messy derailment" to me. Hope that's not the case here!

 

[Tim M]

........ minimise the possibility of causing a 'wrong side' indication during the work - Clapham Junction 1988 is always a reminder of what can go wrong.

Just to clarify, what caused the disaster at Clapham Junction wasn’t an earth fault. It was caused by not cutting back a wire removed during stageworks as part of resignalling.

 

[John Webb]

Just to clarify, what caused the disaster at Clapham Junction wasn’t an earth fault. It was caused by not cutting back a wire removed during stageworks as part of resignalling.

Thanks, I was aware - I was trying to indicate that working on signalling equipment to find even an earth fault can have potential perils if not done correctly.

 

[Taunton]

Thanks, I was aware - I was trying to indicate that working on signalling equipment to find even an earth fault can have potential perils if not done correctly.

One that is more relevant is the Severn Tunnel rear-end collision in 1991, where a second train managed to get admitted to the tunnel on a signal that changed to green while the fault finding team were working on the axle counter equipment.

 

[Belperpete]

One that is more relevant is the Severn Tunnel rear-end collision in 1991, where a second train managed to get admitted to the tunnel on a signal that changed to green while the fault finding team were working on the axle counter equipment.

Wasn't that down to the signaller agreeing to them resetting the axle-counter while there was a train in section? Unfortunately there was no form of co-operative reset, and the axle-counter was shown on the panel pretty much as though it was a track-circuit.

 

[e30ftw]

What is your reason for being intrested in how a S&T team would deal with an earth fault?