Lightening strikes affecting signalling in March area 20/7?

trebor79

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Chaotic and lengthy journey home from Sleaford to East Anglia for me yesterday. Nothing moving from Peterborough to anglia due to lightening strikes on signalling in March area. I eventually got home via Stevenage and Cambridge in time for the last train to Norwich.
But I was surprised lightening would impact the largely mechanical signalling in the March area?
 
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The exile

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Chaotic and lengthy journey home from Sleaford to East Anglia for me yesterday. Nothing moving from Peterborough to anglia due to lightening strikes on signalling in March area. I eventually got home via Stevenage and Cambridge in time for the last train to Norwich.
But I was surprised lightening would impact the largely mechanical signalling in the March area?
presumably wouldn't knock out the mechanical signalling itself (although I suppose a direct hit could fell a signal post) - but could play havoc with the inter-box communication.
 

Bald Rick

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Chaotic and lengthy journey home from Sleaford to East Anglia for me yesterday. Nothing moving from Peterborough to anglia due to lightening strikes on signalling in March area. I eventually got home via Stevenage and Cambridge in time for the last train to Norwich.
But I was surprised lightening would impact the largely mechanical signalling in the March area?

March (East) isn’t largely mechanical. It’s largely electric, albeit operated by levers.

Besides, when I used to do such things, one of my signallers got an electric shock through lightening - he was pulling a point lever at just the wrong moment when lightning hit the track nearby.
 

GB

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Chaotic and lengthy journey home from Sleaford to East Anglia for me yesterday. Nothing moving from Peterborough to anglia due to lightening strikes on signalling in March area. I eventually got home via Stevenage and Cambridge in time for the last train to Norwich.
But I was surprised lightening would impact the largely mechanical signalling in the March area?

Affected Manea, Stonea and Three Horse Shoes. Might be absolute block but still a lot of electrical equipment between them including signals, track circuits and level crossings.
 

LowLevel

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presumably wouldn't knock out the mechanical signalling itself (although I suppose a direct hit could fell a signal post) - but could play havoc with the inter-box communication.

For the last 100 years plus mechanical signalboxes have been very much reliant on electrical equipment. The usual issue is lightning striking the rails blowing up the track circuits and the various bits of kit they're linked to - particularly in that part of the world where the boxes supervise lots of automatic level crossings.

It might not fell a signal post but if it takes out the electric locking you'll not be able to get the lever out of the frame.
 

O L Leigh

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I expect that it was the crossing phones and other related equipment that got affected, as I've been caught up with this sort of issue in the past. There's rather a lot of crossings across the Fens and getting cautioned across each one would take flipping ages.
 

trebor79

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Ah yes, I forgot about all the level crossings and the fact that some of the boxes are effectively electric just with the levers connecting to electrical stuff rather than rods and wires. And fair comment about track circuits, though I suppose in an absolute block system you could get away without them (notwithstanding that there might be very good reasons why it isn't allowed at some locations).
Trains were getting through again by the time I got to Cambridge, but on balance I think I did the right thing (advised to by station staff at Peterborough too) as it guaranteed I actually got home, and I don't think I'd have got the earlier train in any case.
 

Tomnick

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And fair comment about track circuits, though I suppose in an absolute block system you could get away without them (notwithstanding that there might be very good reasons why it isn't allowed at some locations).
A very small number of boxes might have no track circuits, but I don't know if there are any left now. As an absolute minimum, you'd normally have a berth track circuit in rear of each home signal, to guard against a train standing there being overlooked. You certainly can't get away without them just because they've failed - they're an integral part of the signalling system and will (rightly) lock other things.

I have, on one occasion, worked a mechanical box (mostly colour-light signals) for the last few hours of a twelve hour failure of the mains power supply. Everything, including the (large) full barrier crossing just outside the box, worked okay on batteries. The first thing to fail was one of the TPWS transmitters, although the barriers were getting a bit slow by then too! AHBs should have batteries that will last a similar period of time, and even if you lose crossing phones, cautioning for every crossing is slow but at least you can still run a service of sorts!

The trouble with lightning strikes is that, rather than just causing the power supply to fail, they have a tendency to fry things and stop them working altogether!
 

Tio Terry

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I can remember back in BR days changing at Peterborough on a return York to Norwich trip and getting stopped and cautioned at almost every box between Peterborough and Norwich. In those days the AHB's all had flashing "Another Train Coming" neon signs but they were not battery backed up. The lightning had taken the power supplies out and that meant the signs didn't work so cautioned. It took absolutely hours to get back to Norwich.
 

Class 170101

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March (East) isn’t largely mechanical. It’s largely electric, albeit operated by levers.

Besides, when I used to do such things, one of my signallers got an electric shock through lightening - he was pulling a point lever at just the wrong moment when lightning hit the track nearby.

Surprised its not earthed in some way.
 

TSG

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Surprised its not earthed in some way.
It likely is earthed in numerous ways, some intended and some not. However, factors that can be ignored for most purposes (inductance of earth bonds, physical routing of them and the resistance of the ground itself) come into play in a big way when trying to dissipate the vast and sudden energy of a lightning strike. I think mechanical signalling would be a difficult thing to protect well if you designed it with lightning protection in mind, let alone trying to do it 100 years later as an afterthought.
 

Tio Terry

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Earthing things to protect against damage by lightning - and in some cases traction flashover - is quite a complicated subject. There is something called Rise Of Earth Potential (ROEP) to consider and the rate at which this disepates which is affected by the type of soil conditions amongst other things. I did quite a bit of work with this sort of thing years ago, also worked with SNCF staff looking at how they protect their High Speed network against lightning related failures.
 

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