Nexans has worked with Light, Rio de Janeiro’s electric utility, to develop the 'Lo-Sag' conductor, an overhead power line technology comprising a thermal resistant aluminium conductor wrapped around a composite carbon core. Compared with a traditional conductor, which uses a steel core, the composite carbon core of the same diameter is much lighter and 50% stronger.
More importantly, the carbon core’s coefficient of thermal expansion is roughly one tenth that of steel, so it expands (and ‘sags’) much less when heated by the high current flowing in the conductor, enabling safety clearances to be maintained between the conductor and the ground, even at high operating temperatures.
These properties enable the new overhead lines to be driven much harder by the electricity utility. So while a conventional conductor, at a typical safe limit will operate at 90°C, Lo-Sag enables it to carry around twice as much power. This makes Lo-Sag suitable for upgrading existing routes to higher powers, using established routes and existing cable towers with minimal modifications, reducing both project delivery times and costs.
The first Lo-Sag installation has been in operation for six months, with an installation on Light’s 138kV transmission line connecting SE Cascadura to SE São Jose in Pavuna district, an area with a specific need for more electricity.
While Lo-Sag has been developed to meet the particular needs of Brazil’s transmission networks, especially in upgrading projects, the concept is also suitable for other markets around the world. Lo-Sag can also offer important advantages in the construction of new transmission lines, especially for long spans over 1km, enabling a 30% reduction in tower height.