Application of medium voltage cable predictive diagnostics

Industrial plant engineers are required to provide a safe and reliable electrical cable infrastructure that will assure maximum uptime at the lowest possible cost. As electric systems age, engineers are faced with the challenges of lower availability of maintenance crews and high financial costs of cable replacement. In order to optimize these challenges, predictive diagnostic tools can be used to effectively monitor and repair discrete locations to extend cable system life. This paper is an overview covering best practices for commissioning new installations and applying predictive diagnostic programs to aging industrial shielded extruded dielectric cable systems rated 5kV and higher. This paper will examine failure mechanisms in extruded cable and accessories, review the IEEE 400 Guide for Field Testing and Evaluation of the Insulation of Shielded Power Cables, discuss the adverse effects of withstand testing when the objective is to assure system reliability, and present case studies from industrial facilities which demonstrate the ability of defect specific diagnostics to pinpoint defects and avoid future unplanned service outages. Lastly, the use of a taped metal shield will be addressed, examining the aging process that may cause it to be less reliable than other shield designs and limit the ability of the industry to locate failures and assess future cable system performance.