Lorry tears down 25kV cables

[bernardgreen]

Sparks fly as lorry hits power lines at crossing

An explosion and smoke is seen as the vehicle crosses tracks, causing disruption to train services.

www.bbc.co.uk

Interesting that the major arcing is not where the lorry hits the cable but is between the lorry's wheels and the train track.

 

[ericmark]

I have often wondered why one can drive in other than first gear with the tipper raised. One would expect the driver to notice when raised so high, but were only a few inches it would be easy to not realise it had not fully dropped.

I know we have steel wires in tyres, not sure of what is in the rubber type material, I know with wellingtons there is graphite to stop a build up of static, maybe the same with tyres.

 

[SUNRAY]

I have often wondered why one can drive in other than first gear with the tipper raised. One would expect the driver to notice when raised so high, but were only a few inches it would be easy to not realise it had not fully dropped.

I know we have steel wires in tyres, not sure of what is in the rubber type material, I know with wellingtons there is graphite to stop a build up of static, maybe the same with tyres.

Perhaps he was only a few metres from where he fly tipped and was still in quick getaway mode

 

[ebee]

i always wondered why BS7671 gave min heights for overhead cables at crossroads that were more than at other places - was it cos they expected crashes at crossroads to be head on thereby forcing colliding nose end of vehicles to rise up to higher levels?

might have been 5.8m rather than 5.2m or some such amount (colliding vehicles lift 2 foot into the air or something)?

 

[ericmark]

Don't have that problem with local trains, .

 

[Harry Bloomfield]

I know we have steel wires in tyres, not sure of what is in the rubber type material, I know with wellingtons there is graphite to stop a build up of static, maybe the same with tyres.

They have graphite in them,

 

[foxhole]

Arcing will probably be from lowest part of metalwork earthing .

 

[Harry Bloomfield]

They have graphite in them,

The graphite is added, to help make the tyre stronger, more UV resistant and to help discharge static. Given a large enough voltage gradient, the tyre will conduct to ground, especially when travelling over earthed metal rail lines.

 

[SFK]

At that voltage the sparks could simply be the electricity arcing between the metal wheel rims and the tracks.

 

[ericmark]

But it seems there was no RCD protection at 40 mS? I can accept the first flash over, but seems there is a lack of protection there? I can remember being told how thieves were stealing copper, and how they did it, and how the operators would count before resetting the supply so giving time for thief to claim pole then resetting the supply, in the hope of stopping the theft, not in this country by the way, never worked with HV so not sure how faults are detected, but that arcing seemed to go on for far too long.

 

[SFK]

But it seems there was no RCD protection at 40 mS

But I presumed that the line sees no RCD fault as rhe power has gone from the "L" overhead line, through the 'resitive' lorry (that will be seen as an load / train motor), and into the "N" tracks. So no issue to be seen by RCD (until cable falls on ground or hits a pylon).

 

[ericmark]

There must have been an overload with first flash, never mind RCD protection, some thing seems wrong to have not tripped out?

 

[bernardgreen]

I am sure there is no RCD protection possible as the "Neutral" conductor is in poor to good contact with the ground along its entire length,

 

[SFK]

There must have been an overload with first flash

I would argue that the electrical resistance of the lorry limited the power spike to less than that of a Train Engine.
ie, there was no overload with the first flash as that power spike pulled less than normal power load of an operating train.