Investigation into degradation properties of low-viscosity silicone liquid/paper insulation systems for diagnosis in liquid-immersed transformers

Thermal and electrical degradation properties in low-viscosity (20 mm
²
/s, (20 cSt) at 25 °C) silicone liquid and insulation paper were investigated to improve reliability and to enable preventive maintenance technology in transformers. Heat-accelerated degradation in samples of 20 cSt silicone liquid and insulation paper in sealed glass tubes with copper, silicon steel, and pressboard was examined to replicate the environment of the transformer tank. After the examinations, the tensile strength of the paper was measured, and the quantity of decomposition compounds was also measured. It was concluded that diagnosing faults by analyzing decomposition compounds with silicone liquid should be possible in the same way that it is with conventional mineral oil.