Effect of Nanofibrillated Cellulose Doping on Properties of Oil Immersed Insulating Paper during Thermal Aging

To evaluate the performance of Nanofibrillated cellulose (NFC) modified insulating paper under long term running process, 10 wt. % NFC modified insulating paper and ordinary insulating paper were subjected to accelerate thermal aging for 720 hours in a 130°C thermal aging chamber. The aging characteristics and electrical performance were measured during the aging process. Results show that NFC modification can delaying the thermal aging rate of oil immersed insulating paper and enhancing the electrical strength of oil immersed insulating paper during thermal aging process. NFC makes oil-impregnated insulating paper more compact during thermal aging process, resulting in higher polymerization degree and crystallinity. NFC modification can increase the relative permittivity and dielectric loss of the oil-impregnated paper during thermal aging process slightly. The AC and DC breakdown strength of the NFC modified paper are better maintained than the conventional oil-impregnated paper.