Lightning Strikes at Battersea

[John55]

Funny you mention the Empire State, it is designed to cope with lightening strikes because it has rods to attract and redirect the lightening. You seriously suggest we do this with every piece of railway electronics?

Railway electronics (and other equipment) isn't fitted out in the open 1250 ft above local ground level. It is installed within a building as demonstrated by the photograph of the damaged substation someone posted earlier in the thread. Good design keeps the surge outside the equipment rooms and protects the equipment.

The point of lightning protection is to keep damaging surges away from anything which might be damaged (including any staff in the building at the time of a strike by the way). All buildings are required to have a lightning protection system and clearly a building like the Empire State will have a rather more substantial one than most.

A strike on a signal gantry should go straight to earth at the gantry and the protection systems should prevent conducted transients damaging equipment connected to anything on the gantry.

If you think about the mobile phone network it is much more exposed to lightning strikes and doesn't fall over all the time.

 

[A60K]

Well, the railway network doesn't fall over *all* of the time either - when was the last serious disruption caused by a lightning strike, out of interest?

 

[NSEFAN]

Railway electronics (and other equipment) isn't fitted out in the open 1250 ft above local ground level. It is installed within a building as demonstrated by the photograph of the damaged substation someone posted earlier in the thread. Good design keeps the surge outside the equipment rooms and protects the equipment.

The point of lightning protection is to keep damaging surges away from anything which might be damaged (including any staff in the building at the time of a strike by the way). All buildings are required to have a lightning protection system and clearly a building like the Empire State will have a rather more substantial one than most.

A strike on a signal gantry should go straight to earth at the gantry and the protection systems should prevent conducted transients damaging equipment connected to anything on the gantry.

If you think about the mobile phone network it is much more exposed to lightning strikes and doesn't fall over all the time.
Today 17:47

Equipment doesn't have to be very high up for it to be at risk. I've heard a story of a school which had networking cables installed along a flat roof, and a lightning strike hit them and tore the cables out of the walls until it found ground! Given there is a lot of cabling in the railway signalling, it would be hard to cover up every possible weak spot.

I suspect a similar thing would happen if there was a strike on the overhead wires. The energy has to go somewhere, so until it finds ground it's going to pass through anything in the way.

For all we know, mobile masts might be quite prone to risk of lightning strikes, and it doesn't affect us as much. If a single mast is taken out then the worst that happens is people lose signal in a cell, and pick up signal again as they travel around into another cell.

 

[swt_passenger]

All buildings are required to have a lightning protection system...

Please explain where I'd find one on my house?

 

[Bald Rick]

To my knowledge there is no exposed 'high' voltage electrical equipment that is designed to take a 2 Million volt direct hit without damage. So when lightning hits the 3rd rail or distribution equipment, it goes right through the system blowing everything in it's path until the voltage dissipates. Communications towers, Empire State buildings etc do not have their electrical components exposed.

However lightning does hit the railway, and near to it, relatively frequently. A lot of study has been done to find out how to protect kit. SSI areas are particularly susceptible, so on busy line something called a 'furze' unit acts as lightning protection in every location case. This acts like a giant fuse, and although the signalling can trip out, it can be restored by resetting or replacing a few modules (a 10 min job when the team get to site) as opposed to rebuilding the whole location case (24 hour job). This is what happened at Elmstead Woods yesterday afternoon.

What happened at Stewarts Lane at 1730 yesterday was a direct hit of the traction distribution equipment. It's pretty difficult to protect against that sort of thing, in the same way that it's pretty difficult to protect your TV from a lightning strike on your aerial if you HAVE to have the TV on.

Here endeth todays sermon.

 

[TW7]

The study of the effects of lightning on electronic and electrical equipment is well advanced and effective techniques for minimizing the effects are available.

There is no reason for lightning to cause this level of disruption to the railway network. I expect when the reasons for these failures is identified there will be a failure of design or installation. The usual reason for destructive damage in my experience is unauthorised modifications to the equipment protection or failure to maintain it.

Unfortunately the signalling equipment cannot be protected against such a sudden and powerful surge of volts and amps.
The TP hut at Linford street being struck and set alight was just pure bad luck.