A comparative analysis of different dielectric fluids for cable sealing ends

A Review on the Relevance of Standards for Silicone Insulating Liquids Used in Cable Sealing Ends

“…Recent research on the comparison of liquid dielectrics for insulation in CSE showed that silicone liquid has a lower affinity to moisture. The results indicate that the changes in chemical and dielectric properties of moisture-aged silicone liquid are negligible at 125 ppm moisture content [5]. Research undertaken by Liland et al on 100 CSE in Norway confirms this and found that the mean moisture content was around 90 to 100 ppm [32], which is double the saturation limit of mineral oil.…”

“…This is also one of the reasons why e.g. ester-based insulation liquids require transformers to be redesigned, in order to account for the significantly different viscosity [5]. For CSE, on the other hand, this requirement is not critical, since the CSE does not require the liquid to be circulated within cooling channels.…”

“…They are considered "maintenance free". This is, in part, due to the exceptional chemical, thermal and dielectric properties of the silicone liquids which are frequently the liquid insulator within CSE [4], [5]. Over the last two decades, there have been issues reported with XLPE CSE of different designs and manufacturers, with few consistent features between the designs and failures.…”