Abstract
In this study, three types of silicone rubbers, namely, insulative silicone rubber, conductive silicone rubber and silicone rubber with conductive as well as insulative layers are investigated for their compatibility with mineral oil. Mineral oil with different silicone rubber samples is thermally aged at 130 °C for 360 h, 720 h and 1080 h and at 23 °C, 98 °C and 130 °C for 360 h. At the end of each ageing interval, mineral oil and oil-impregnated silicone rubbers are investigated for their dielectric properties. Aged mineral oil samples are investigated for their moisture content, breakdown voltage, colour number, dissolved gases and total acid number, whereas solid insulation samples are investigated for their moisture content. Additionally, pressboard samples in mineral oil and mineral oil without any solid insulation materials are also aged under the same conditions and are investigated for their dielectric properties. From the obtained results, it can be assessed that the presence of carbon particles in conductive silicone rubber negatively impacts the dielectric properties of mineral oil. Among the investigated silicone rubbers, the insulative silicone rubber exhibits good compatibility with mineral oil and a strong potential for being used in mineral oil.
Highlights
In this study, three types of silicone rubbers, namely, insulative silicone rubber, conductive silicone rubber and silicone rubber with conductive as well as insulative layers are investigated for their compatibility with mineral oil
The design of the insulation system is considered as the heart of any high voltage equipment design
Natural esters are safe to use at high temperatures and are environmentally friendly, whereas Nomex papers are made of aramid polymers which are high temperature materials with good chemical stability
Summary
Three types of silicone rubbers, namely, insulative silicone rubber, conductive silicone rubber and silicone rubber with conductive as well as insulative layers are investigated for their compatibility with mineral oil. At the end of each ageing interval, mineral oil and oil-impregnated silicone rubbers are investigated for their dielectric properties. Pressboard samples in mineral oil and mineral oil without any solid insulation materials are aged under the same conditions and are investigated for their dielectric properties. Pressboard and paper along with mineral oil are used as insulation materials in high voltage equipment [1]. It has been observed that pressboard and paper degrade at a higher rate when operated at high temperatures This degradation of insulation materials can result in premature failure and thereby reduce the lifetime of the equipment. Natural esters are derived from renewable plant sources and are called as vegetable oils They are biodegradable and have high flash points. Yue et al investigated polyphenylene sulphide (PS), polycarbonate (PC) and polyester film (PET) for their electro thermal ageing characteristics over various ageing durations and ageing temperatures; the obtained dielectric characteristics of these samples
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