Challenges to characterizing failure for naturally and artificially aged wire and cable insulation

Cables and wires are extremely reliable. However, they haven’t existed long enough to reach the wear-out phase commonly known in reliability engineering. This raises many cable failure age-related questions: what performance differences exist between new cable pulled off the production line today and aged cable that has been in service for 60 years; how have changes in cable and system designs over the past century affected cable failure; do the changes in processing and composition result in different failure modes, mean time to failures, or mean time between failures? There is a need to create accurate reliability and lifetime predictions for wires and cables to ensure safe and smooth replacement efforts for the billions upon billions of meters of cable worldwide. These predictions start with understanding insulation structure-property relationships. Unfortunately, the insulation's chemical composition, the primary variable in determining structure-property relationships, is nearly always proprietary information. Similar statements can be made about insulation and cable design and processing criteria. This talk discusses the challenges faced when characterizing cable insulation and additional factors that come into play when characterizing aged insulation. The assessment provided will focus on the structure-property relationship of cross-linked polyethylene-insulated copper conductor cables for primary use in electric vehicles.