Nasty Shock

Posted in Tubeworker's blog on Mon, 03/10/2005 - 13:21,

While attending a tunnel telephone failure at a remote substation, a technician was electrocuted. The shock happened when he opened the cabinet housing the TT equipment.

He was lucky (yes, really). Because he had never been to this particular substation before, he had asked a workmate to go along. His workmate was able to catch him when he fell, and to raise the alarm and get medical attention. Without this assistance, he could have been seriously injured or even killed.

To get to the cabinet, you have to stand on the metal stairs leading to the upper level and reach across to open the cabinet doors. So if – as in this case – the copper TT wire is broken and lying on the positive rail, a path is formed through the equipment in the cabinet, through the cabinet via the door, through your body and to the metal stairs.

The shock knocked him off the stairs. The cabinet door became wedged on the stairs and started to weld itself to the handrail. This caused the traction current in the section covered by the substation to fall.

There must be an immediate enquiry into this appalling incident. The access to the TT cabinet can surely be made more safe. And until things can be improved, no-one should attend this location alone.

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Looking more deeply into this issue ... When traction current dips and no-one contacts line control to say why, then the controller will attempt to recharge the juice after seven minutes.

So in this case, if the technician had been alone, then if the first shock had not killed him, then subsequent recharging attempts might have done.

Cast your mind back to 7th July. When the bombs went off, the traction current fell, and for around 45 minutes, it was thought to be a power supply problem rather than bombs. With passengers climbing out of wrecked carriages and trying to escape along tunnels, attempts to recharge the juice could have added to the death toll.

Surely we need a rethink of the seven-minute rule.

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