Characterization of oil-immersed polymeric blends under DC and AC high voltage

Summary form only given. Recently, the trend of using insulating materials having higher temperature ratings higher than cellulose increases to fulfill the design requirements of high-temperature oil-cooled power transformers. Both the design and weight are essential considerations for some specialized applications of such transformers. Several polymer blends supplied from different manufacturers are characterized in different types of transformer oil under high electrical and thermal stresses. Many factors are experimentally investigated to show their effects on the characteristics of current density vs. electric field (J-E), electrical conductivity vs. reciprocal temperature (σ-T^-1), relative capacitance (ratio of capacitance of impregnated to unimpregnated samples) vs. temperature (C/C₀-T) and the time dependence of the relative capacitance (C/C₀-t) and the charging current (I_c-t). These factors are the type of oil and polymer, type and polarity of the applied voltage and oil temperature. The results show that some samples are unsuitable for use in transformer oil due to they are suffering from substantial physical degradation