Performance Analysis of Alternative Solid Dielectrics of Power Transformers with a Blend of Mineral and Silicon Oils

Abstract

ABSTRACTIn the present paper, the influence of accelerated thermal ageing on the performance of thermally upgraded Kraft, Nomex 910 and Nomex 410 alternative solid dielectrics of transformers in conjunction with mineral oil has been investigated. Subsequently, the characteristics of the solid dielectrics which are impregnated in a blend of 80% mineral and 20% silicon oils are also studied. To investigate these properties, accelerated ageing tests have been carried out at different temperatures ranging from 100 to 220 °C. Furthermore, several electrical and thermal properties of transformer oil which include breakdown voltage, interfacial tension, water content, absorption coefficient and colour factor have been determined. It has been revealed from the test results that Nomex oil-impregnated samples have better thermal characteristics and oxidation stability than the thermally upgraded Kraft oil-immersed samples. Moreover, it is also found from the diagnostic test results that a combination of mineral and silicon oils in conjunction with Nomex insulations has improved characteristics than the samples which are composed of these dielectrics and normal mineral oil. Therefore, Nomex insulating materials and a mix of mineral and silicon oils are suggested as alternative solid and liquid dielectrics for power transformers in order to achieve better oxidation stability, improved thermal characteristics for long service run, reduced operating and maintenance costs. It is envisioned that the present experimental study shall be very beneficial for the utility managers and the end-users of transformers.