A bird caused the closure of the West Coast main line at 13:30 on Tuesday 7 April when it landed on the overhead wires just north of Carlisle.
Normally, that’s not a problem. The bird is only touching the wire, and nothing else, so the 25,000-volt electrical supply is unaffected. Birds sit on wires all the time. They are temporarily charged to the voltage in the wire but, as they are surrounded by air, a good insulator, there is no effect.
However, this unfortunate bird landed on the wire underneath a bridge at Kingmoor. The bird, now charged at 25kV, effectively reduced the gap between the electrical supply and the bridge. This earthed the system, passing a high current into the bridge through the bird, which won’t have survived. The high temperature caused by the short melted the cables, which then lost tension and broke away from their supports.
The West Coast main line, which runs from London Euston to Scotland, is one of the busiest routes in the country. Even in these times of restricted travel, the line moves one million tonnes of freight each week. So, engineers hurried to make repairs.
Mindful of the need to distance themselves, a crew of twelve worked for six hours to repair the cables, re-tension them and test the circuits. They also fitted secondary isolation on the wires under the bridge so they do not earth in the same way again, which will help protect birds in the future.
Darren Miller, Network Rail infrastructure and maintenance delivery manager for Lancashire and Cumbria, said: “With the movement of essential goods on the railway like medical supplies, food and energy, it was vital we fixed this problem as fast as we possibly could.
“We’re sorry to any passengers or freight customers effected by the delay while we worked hard to repair the damaged power lines. However, our specialist engineers safely completed the repair in time for the night-time freight traffic that transports essential food, fuel and medical supplies across the country.”