Introduction: The breakdown pathways and kinetics of poly-dimethylsiloxane (PDMS) insulating fluids are not fully understood, and the study and deeper understanding of how these fluids behave under electrical stress may lead to the identification of significant components which may be used to determine the early determination of fault activity within silicone fluid filled terminations. It is envisaged that with the chemistry fully understood, a much greater appreciation of fault level and time to failure will be derived.

Furthermore, the identification of selective analytical markers of fault activity will allow simple routine testing methods to be migrated to the contract oil laboratory, enabling National Grid to look for fault symptoms in a similar way to that already practiced for instrument transformers and bushings

Objectives: To simulate, in the laboratory, the degradation processes seen in silicone oil insulated cable sealing ends and to develop a sufficient understanding of these processes to facilitate the analysis of samples taken from the field in order to provide a measure of asset health.