Development of a new solid insulation for liquid-immersed transformers

DuPont Nomex® 910 engineered cellulose insulation is a new unique, solid insulation material composed of high quality electrical grade cellulose pulp and web like binders made from high-temperature aramid polymer. The technical feasibility of this new generation paper has been investigated, resulting in a paper composed of high quality aramid fibrid rather than synthetic fiber and binder, with a multi-ply construction of cellulose and aramid. The combination is also economically advantageous. Initial performance testing with pilot plant size paper shows thermal capabilities of at least 10°C above the incumbent thermally upgraded kraft cellulose paper, raising hot spot operating temperatures of a transformer up to 120°C. This paper is expected to be launched as a key player in liquid-immersed transformer applications for interlayer insulation in distribution and turn insulation in small power transformers.