New developments in solid dielectric life extension technology

Abstract

Twenty years have elapsed since the field introduction of the first solid dielectric enhancement technology. During those twenty years, this technology has proven itself as an important tool to enhance the reliability of aging infrastructure. Incremental improvements during those twenty years have aided in the widespread commercial acceptance of the technology on at least four continents. There are some concerns with the current technology, which has been utilized by over 150 utilities worldwide. These include: (1) A higher than desirable post-injection failure profile, due to the slow permeation of the fluid into the dielectric and the resulting slow increase in dielectric performance after injection of approximately 0.5% per day, (2) a limited cable life extension of 10-20 years as suggested by, (3) safety and operational issues related to the low flash point (-5.5 /spl deg/C), and (4) the corrosion of aluminum conductors that occasionally results in failure of treated cables caused by high concentrations of methanol by-product of the most widely-used treatment fluids. A novel approach, which includes new installation methods and new materials to extend the life of power cables, is described. Theory and experiments are discussed which demonstrate that the new approach addresses all of the current shortcomings associated with the first generation technology. In comparison to the technology employed over the last two decades, the new technology provides: (1) More rapid short-term reliability the post-injection dielectric performance improvement slope is greater than an order of magnitude steeper, (2) longer rejuvenated cable life approaching the 40 year expected life for the highest performance modern cable designs, (3) an inherently safer installation, including lower flammability fluids, which have flash points in excess of 65 /spl deg/C, and an injection paradigm, which dramatically reduces the likelihood of electrical contact, and (4) compatibility with all aluminum alloy and copper alloy conductors.