Application of polyamide papers in liquid-cooled transformers

The 60 Hertz and impulse electrical strength of oil impregnated polyamide paper is as good as that of high quality electrical grade kraft paper and better than that of rope-kraft paper used as conductor insulated. The 60 Hertz dissipation factor of polyamide paper in oil increases moderately with increasing temperature. Based on burst strength and tensile strength retention, the thermal stability of the polyamide paper is substantially superior to that of cellulosic paper when aged in oil or askarel at 150°C and 175°C. Polyamide paper showed little or no degradation after extended life tests in distribution transformers. Polyamide paper with its superior mechanical properties can better withstand manufacturing operations in production than can cellulosic papers. Based on life test results the polyamide paper will permit the design of transformers with higher operating temperatures and greater overload capacities than can be obtained using cellulosic paper.