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NEW, ONE-PART SHEAVE OF DELRIN FOR PREFORMED DEAD ENDS ON EDF'S OPGW CABLES
Switching to a single, injection moulded part of DuPont Delrin acetal resin has enabled French Optical Ground Wire hardware manufacturer Dervaux SA to reduce production costs by one third on the preformed dead end pulley sheaves for OPGW cables that it supplies to energy giant Electricité de France. Dervaux Design Engineer, Fabien Camelio, says that Delrin was selected for this application because of the acetal resin's excellent mechanical strength (withstanding up to 120,000 Newtons), its resistance to nature's elements (rain, snow, ice, hot sun, etc.) and its outstanding electric insulation properties. The sheave of Delrin must also withstand short-term exposure to 85 degrees C in the case of a short circuit, according to EDF's demanding specification (D6100.0677/90.27c). More than a thousand pulley sheaves of Delrin have been in place on EDF pylons throughout France since 2000 with not one problem reported, attesting to the success of this application. The sheaves are manufactured by Dervaux in accordance with IEC 61284, the international standard for accessory parts on aerial cables. Dervaux's preformed dead ends are essential to the pulley system that mounts or 'hooks' OPGW cables onto EDF's pylons throughout France. OPGWs protect conductor cables at the top of pylons from short circuits or lightning in the case of electrical storms. The sheaves of Delrin (outer diameter: 200 mm, height: 56 mm, weight: 750 g) ensure optimal mechanical connection between the preformed dead end clamp and the rest of the OPGW, and insulate the preformed dead end from the tower or pylon. Once mounted, they play a critical role in protecting and maintaining the long life of the cables for several decades. The dead ends can be mounted onto OPGW cables with either diameter of either 15.3 mm or 19.2 mm). They consist of three parts: reinforcing rods of aluminium; clamps of steel and the sheaves, which until now were constructed in two parts of aluminium and a low performance plastic. According to Dervaux, this is the first time worldwide that dead end sheaves for OPGW pulleys have been made in one part. The significant production cost saving Dervaux has achieved has enabled it to pass corresponding savings on to EDF. Dervaux SA of Le Chambon-Feugerolles (France) manufactures EHV switchyard connectors, EHV line accessories and formed accessories. Its facilities are certified according to the ISO 9001 standard. Dervaux SA is part of The Sicame Group, a global company with headquarters in France. Formed in 1958, the group specialises in accessories for electrical transmission, electrical distribution, street lighting, electrical safety products and compression tools and connectors.
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