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Overhead Transmission Line Category III Check

Eadon Consulting carried out the independent category 3 check of the access gondolas used for working on overhead power lines. Replacing the conductors between electricity pylons carries many risks, particularly when the transmission lines cross a road or railway. Traditionally, scaffolding structures are erected over the route to protect it in the event that one of the conductors breaks as the new cable is pulled in. This is costly and time consuming.

Key facts

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Location

Suffolk

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In Partnership with

Babcock Networks Division

Babcock Networks Division have developed the Skysafe system – their own innovative alternative to scaffolding constructions, which will prevent cables from falling if they break at a fraction of the cost in time and money. The system supports the conductor during replacement using independently anchored ropes and a series of trolleys. Eadon Consulting were commissioned to carry out a third party check on the use of this system over a railway line in Suffolk.

Eadon Consulting independently derived the loading conditions for the temporary works, including wind and ice loading on the pylons and cables in accordance with the Eurocodes. These loadings were then applied to a series of non-linear cable models representing different stages of Skysafe deployment and use. This allowed each cable to be checked for tension and sag, ensuring the cable would not break and that sufficient clearance was maintained from the railway’s overhead line equipment.

The temporary works imposed additional loads on the pylons at each side of the span, and so they were checked against BS EN 1993-3-1 – Design of Towers, Masts and Chimneys.

Eadon Consulting were able to carry out a thorough check rapidly, which revealed no problems. Work proceeded safely on site without any issues.