Crystalline thermoplastic wound tapes for submarine cable insulation - providing low porosity, high capacity, deep water cable insulation

摘要

Conductors of electric cables are insulated by overlapping winding of a tape. The tape is a pore- and void-free and 200 mu thick and is wound under sufficient tension to obtain coherent grip, i.e., no-slip between adjacent or overlapping layers. The tape is made of a highly crystalline (40-90, pref. 50-80%) polymer having a high wt. average mol. wt. (2-7 x 105, pref. 3.5-5 x 105) with high strength (=5 daN/mm2) and elastic modulus (175-450 daN/mm2). The tape is suitable for cables used underwater at =500 m. for power capacities =1000 MW. It is similar to oil-impregnated paper wound insulation. Extruded coatings are slow to apply and so porous that max. immersion depths are 500 m. and power loadings 300 MW.