EPR-based URD insulation: a question of confidence

Concern about the possibility of failure of miles of medium voltage (15-35 kV) underground residential distribution (URD) power cable is discussed. This concern centers on the cable specification decisions that were made years ago an the consequences of cable failure and subsequent replacement. The factors that degrade URD are recalled. Choice of insulation material is discussed. The effects of thermal conductivity and thermal expansion are examined. Accelerated cable life test (ACLT) results are considered in the context of the debate over ACLT vs. underground testing. It is concluded that ethylene-propylene rubber (EPR) has performance characteristics that permit cables to be used successfully under conditions of electrical stress, heat, and moisture, and that outstanding performance in ACLTs of cables insulated with EPR-based compounds is obtained.>