Evolution of medium voltage extruded cable technology in north america

When unjacketed medium voltage (MV) extruded power cables were first installed in the late 1960´s, cable manufacturers and utilities expected them to perform reliably for 20 or even 30 years. History has shown that the service life of some of these early cables, whether HMWPE or EPR, could be improved. Since then, utilities in North America have demanded and obtained significant improvements in the performance and reliability of MV underground cables. Improvements in insulation cleanliness and resistance to wet aging, in semiconductive shield smoothness and cleanliness, in cable jacketing, in cable manufacturing processes, and in specifications and qualification test requirements, have all combined to deliver in modern cables expected service life exceeding 40 years. Many accelerated cable aging tests, as well as more relevant field aged cable tests, have been conducted in the last decade and confirm the improved reliability resulting from the material and cable manufacturing improvements. Results from key studies will be summarized. The paper will also discuss further improvements being targeted in the development of new products.