A transformer assembly is provided that includes a housing, transformer oil disposed within the housing, a plurality of coils of electrically conductive wire, and aliphatic polyamide insulation material operable to insulate the coils disposed within the oil. The plurality of electrically conductive coils is disposed in the housing and in contact with the transformer oil. The aliphatic polyamide insulation material includes stabilizing compounds and nano-fillers. The stabilizing compounds provide thermal and chemical stability for the insulation material.