The condition monitoring of fluid-filled taped cables employed in underground transmission through dissolved gas analysis

There is an urgent need to monitor the condition of fluid-filled taped (FFT) cables. The dissolved-gas analysis (DGA) technique that has been successfully applied to power transformers holds great potential for the preventive maintenance of FFT cables. However, before this emerging technique can be properly applied to cables, a suitable fluid sampling and subsequent gas analysis method had to be developed, including the generation of both laboratory and field data to aid in data interpretation. Data on gas saturation levels in various cable fluids have been presented. This paper describes a novel method developed specifically for FFT cables and discusses field results so obtained. The type, distribution and concentration of gases from fluid alone and paper alone under electrical stress has been presented, including the differences between normal and not-so-normal cable systems as demonstrated by DGA. The concept of wet tensile strength has been introduced to the cable industry and it holds promise to serve as a cable aging indicator. DGA can successfully identify problem cable systems. Further work is in progress to refine the DGA technique and determine the remaining life of taped cables