Review of International Standards and Practices for Medium Voltage Power Cable Diagnostics

Medium voltage underground distribution cables represent a large investment for electric utilities worldwide. In many utilities a significant percentage of these cable circuits are over thirty years old and may be approaching the end of their estimated lives. As a result utilities are now being faced with important decisions to maintain, repair, refurbish, or replace their cable systems. These decisions should not be made based on age alone as cables do not age uniformly with time or age uniformly along the length of a cable circuit. Thus, we need to determine the condition of cable systems, and in particular, the electrical insulation by means of diagnostic tests, so that a sustainable asset management program can be established. This paper reviews cable ageing mechanisms, the different diagnostic technologies available to utilities, and also compares the standards that have been, or are, under development in North America and in other parts of the world.