France's network of medium- and high-voltage electrical lines traverses 105,000 kilometers and is owned and maintained by RTE
(réseau de transport d’électricité), a subsidiary of EDF (Electricité de France). The company's aerial service, STH (Services et Travaux Héliportés), is responsible for the surveillance, maintenance, and construction of the network via a fleet that includes H225
, AS355, H135
, and H125
In order to serve customers with the least interruption to services, STH has developed innovative ways of carrying out heliborne operations on high-tension lines, relying on the work of specially-trained pilots and technicians. Known as “lignards,” these technicians are regularly lowered in cradles suspended below a helicopter to perform maintenance work without cutting the electrical current, which can range from 64,000 to 400,000 volts.
At least once a year, every kilometer of the 105,000-kilometer network is paid a visit. This lets STH detect anomalies in the network which would later be subject to repairs by maintenance staff.
“The work requires highly specific skills,” said Christophe Berassen, director of STH at RTE. “These line-repair operations performed without cutting the current, with people working from cradles, is really a synergy between electrical skill and aeronautical skill. That’s the key—the reliability of the aircraft, and the advanced skill level of the people doing the job.”
Preventive maintenance is equally high among STH’s activities. Using thermo-infrared cameras to pinpoint hot spots between cables and conductors, technicians know where to plan for specific maintenance.
As the network extends across congested zones which necessitate the extra security and performance of twin-engine helicopters, fleet modernisation is ongoing. This year, two new helicopters – an H125 and H135 – will join the stable. “We enjoy a strong partnership with Airbus Helicopters and engine-maker Safran Helicopter Engines,” said Berassen. “We’re looking for the greatest reliability and availability in what we do. Ensuring safety during missions is the most essential aspect of what we take into account, every day.”
To accompany the growth and evolution of RTE’s heliborne services, a new site is under construction at Avignon airport. From 2017, the new site will be able to house the whole of the company’s heliborne facilities, as well as those of their subsidiary, Airtelis, who ensure the external commercialisation of heliborne activities.
With the exception of two H225 helicopters owned by Airtelis and used for heavy-load work transporting pilons, unrolling cables, and carrying construction materials, the fleet of helicopters flying the lines belongs entirely to RTE.