Analysis of gasses generated by electrical discharges in low viscosity silicone oil

Silicone oil has merits of less flammability and excellent environment-friendliness. High-viscosity silicone oil of 50 cSt has been widely applied to power and distribution transformers. Recently, application of low-viscosity silicone oil of 20 cSt to transformers has been considered for its excellent cooling performance. Detection of incipient fault conditions in low-viscosity silicone oil immersed transformers becomes more important when they are operated in electric power systems. Detection of certain gases generated in a transformer is usually the useful indication of an abnormal condition. To clarify its applicability to a low-viscosity silicone oil immersed transformer, this paper described gas characteristics generated by electrical discharges in detail. It was clarified that the identification of abnormal conditions are possible by considering the amounts and types of generated gases. Finally, gas characteristics were compared with those in 50 cSt silicone oil and mineral oil.