Experience with condition assessment studies on 230kV SCFF cables in the BCTC network

This paper highlights some of the work undertaken to assess transmission cable assets and explore up-rating opportunities of two 230 kV self-contained fluid-filled (SCFF) cable circuits within the British Columbia Transmission Corporation (BCTC) Network. It highlights all the work that was undertaken as part of the condition assessment studies for these cable systems. A systematic study was undertaken to examine the issues that could potentially affect all or some of the dielectric, chemical, or thermal performance aspects of the cable system. Historical maintenance data that was available on these assets were carefully examined. Following this comprehensive review a series of the "gaps in knowledge" were identified. A systematic program was developed to help fill such "gaps in knowledge". As an example, sampling ports were installed on several normal and stop joints along this cable corridor to ascertain both gas-in-fluid concentrations (DGA) and fluid dissipation factor (DF) measurements. Sheath bonding studies were performed to compare the predicted and measured bond currents and determine potential causes for these observed anomalies. This paper provides some of the results obtained to date, some of the remedial measures adopted and some of the challenges that were encountered during the course of project execution; some the observations included (a) high sheath currents (b) higher than normal concentrations of acetylene and hydrogen in dissolved gas in fluid analyses. It also focuses on some of the measures adopted and the successes and challenges that they presented. A discussion on data obtained with preliminary modifications to the sheath bonding design provided very encouraging results but it also presented some challenges.