Effect of Applied Electric Field on Conductivity of Synthetic Ester Impregnated Kraft Paper

Synthetic ester has emerged as an alternative to mineral oil due to its environmentally friendly and fire safety features. This paper assesses the applicability of synthetic ester in converter transformers from the perspective of conductivity of synthetic ester-impregnated paper, which affects electric field distribution and hence the design of converter transformers. Experimental studies unravel the effect of applied electric field on conductivity of synthetic ester-impregnated paper, i.e. a positive correlation exists between the short-term conductivity and applied electric field, whilst the long-term conductivity exhibits a non-linear trend. Key parameters describing space charge transport in synthetic ester-impregnated paper are identified and compared with those of mineral oil-impregnated paper. Simulations allow the intrinsic and injected charge carriers of synthetic ester-impregnated paper to be quantified, and reveal space charge phenomena under different applied electric fields and their effects on conductivity.