Safety and overhead power lines National Grid is best known in the public mind for the network of overhead power lines it manages across most of the UK.

The safety criteria for operating overhead lines are stringent and include the physical proximity of overhead lines to their surroundings and to each other, as well as the tension to which lines are subjected – a major factor in their ageing.

Software to model tension and sagging

National Grid contracted OCC to provide software to model the tension and sagging of overhead lines under different conditions including span length, creep, temperature, wind speed, ice loading and the profile of the ground.

The geometry of a freely hanging cable is called a ‘catenary’. Determining the properties of this shape was a historic mathematical milestone. First proposed, in the form of a Latin anagram, by Robert Hooke, the discovery that the optimal shape of an arch is a catenary flipped upside down was used by his colleague Christopher Wren in the rebuilding of St Paul’s cathedral. Overhead power lines present a complicated series of catenaries.

Delivering benefits

The Tensag client is a Windows .NET app running on the National Grid desktop. The project established a common database of overhead line data and audited runs of safety calculations. This allows maintenance and construction to be more efficiently planned. The only benefit not delivered by this project is an exciting name.