Techniques to Monitor the Aging of Silicone Oils

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

“…The standard suggests many possible techniques for assessing the liquid and gives some values expected for service-suitable liquids. However, this standard suggests that DC conductivity measurements performed according to IEC 60247 are suitable methods for silicone insulation liquids, which contradicts our recent findings, discussed briefly below and published elsewhere [4].…”

“…Thus, the utility of viscosity measurement is limited as an identifier for ageing processes or contamination. A recent review highlights possible alternate chemical analysis, which could perform more accurate analysis faster and with lesser sample requirements [11].…”

“…The report suggests that contaminated liquid turns into a partial gel-like solution [15]. Reports also suggest that for new liquids with viscosity much higher than the standard specified values are being used in practice for CSE [4]. Such a varying range of acceptable viscosity values shall be considered while extending the application of current standards for silicone liquids used for CSE.…”

“…Concerns surrounding the feasibility of measuring the DC conductivity of silicone liquids for CSE, respectively any material with such a low conductivity, have been published elsewhere [4]. The applicability of the test cell set-up described in IEC 60247 and ASTM D1169 [16], [28] were assessed using finite element modelling in order to establish the measurable current.…”

“…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.…”