A field survey of transformer oil quality

REDUCTION of power transformer insulation by the recently recommended two full basic insulation levels1 has placed renewed emphasis on oil quality. The design of corona-free transformers has eliminated the use of sharpedged electrodes in highly stressed locations, favoring the more uniform dielectric field conditions. Because contamination in these uniform fields has a much greater influence on dielectric strength that in nonuniform fields, the question of oil quality is of further importance.