From Impregnated Paper to Polymeric Insulating Materials in Power Cables

As in many other electrotechnical fields, the research work and the early realizations in the cable field during the second half of the last century were the germ of most of the techniques developed in the 20th century. For more than 70 years, paper impregnated with oilresin compounds or simply with oil, prevailed as an insulating material in cable manufacturing, though rubber insulated cables were also used to some extent. The OF cable technique is going on its road towards very high voltages and ratings. It was in the 1960's that the use of extruded polymeric materials, either thermoplastic or thermosetting, made rapid progress. Since then, the most prominent material has been polyethylene, either pure or cured, but the use of ethylene-propylene rubber is also developing. Cables with extruded synthetic insulation are now on the point of meeting all the current needs, from low voltage to the higher existing transmission voltages, with an unequalled ease of installation and operation and a reliability that can already be regarded as quite satisfactory.