Lightweight cable technology helps address Brazil’s power demand

A global cabling project has proved the adage ‘Necessity is the mother of invention’. As a result of economic growth, Brazil’s large cities are experiencing an increased demand for more power and a number of upcoming international sporting events has further increased this demand. But creating new power routes in densely populated areas is proving to be difficult as building new overhead transmission lines is severely restricted and needs controlled clearance to buildings or natural obstacles.

Cable company Nexans has spent five years developing the Lo-Sag conductor, which consists of a thermal-resistant aluminium conductor wrapped around a composite carbon core. The technology was developed at Nexans’ technology centres in France and Belgium.

According to Nexans, when compared with traditional steel core ACSR (aluminium conductor steel reinforced), a Lo-Sag composite carbon core of the same diameter is much lighter and 50% stronger. Significantly for Brazil’s unique situation, the carbon core’s coefficient of thermal expansion is roughly one-tenth that of steel, so it expands - and therefore sags - much less when heated by the high current flowing in the conductor. Even at high operating temperatures, Lo-Sag enables the vital safety clearances to be maintained between the conductor and the ground.

Nexans says these properties mean the overhead lines can be driven much harder by the electricity utility. While a conventional conductor will operate safely at 90°, Lo-Sag can carry about twice as much power. According to Nexans, Lo-Sag is suitable for upgrading existing routes to higher powers, using established routes and existing cable towers with minimal modifications and reducing delivery times and costs.

Nexans worked with Light, the Rio de Janeiro electricity utility company, to develop and install the Lo-Sag conductor in Brazil. The companies installed Lo-Sag on Light’s 138 kV transmission line that connects Cascadura to São Jose in Rio’s Pavuna district.

“In this initial installation for Light, Lo-Sag has been proved to increase the power transmission capacity by 72.5%,” said Sidnei Ueda, OHL application Engineering Manager at Nexans.

“It has been a truly Nexans global project, with the composite carbon core manufactured in France, the thermal-resistant aluminium produced in Brazil and the entire conductor assembled in a Belgian plant.”

While this particular installation was developed specifically for Brazil’s transmission networks, Nexans says the concept is also ideal for other markets around the world. The lightweight core allows spans of up to 2.5 km, reducing the number of pylons required and lowering the height and cost of towers when spanning wide rivers. According to Nexans, towers used with Lo-Sag could be up to 30% shorter.

And Lo-Sag is built to last, Ueda says: “Lo-Sag is expected to have a lifetime of at least 40 years. That is similar to, or even better than, conventional conductors.”