A new kind of transformer oil-based nanofluids(NFs)with semiconductive ZnO nanoparticles is prepared to investigate the influences of adding nanoparticles on relative permittivity of transformer oil. How the NF relative permittivity depends on nanoparticles' volumetric concentration and environmental temperature is also discussed. A nanoparticle polarization model following Clausius-Mossotti equation is proposed. Experiments show that the ZnO NF relative permittivity linearly increases with nanoparticles' volumetric concentration and linearly decreases with temperature. The calculation with the nanoparticle polarization model coincides well with the experimental data. The further analysis for the proposed model suggests that NF relative permittivity is dominantly determined by ordinary transformer oil
while the higher relative permittivity of NFs than pure transformer oil mainly results from the inner polarization of nanoparticles.
YANG Lijun, LIAO Ruijin, SUN Huigang, et al. Investigation on properties and characteristics of oil-paper insulation in transformer during thermal degradation process [J]. Transactions of China Electrotechnical Society, 2009,24(8):27-33.
SUN Jianfeng, GE Rui, ZHENG Li, et al. Analysis of state grid safety operation in 2010 [J]. Electric Power, 2011,44(5):1-4.
CHOI U S. Developments and applications of non-Newtonian flows [M]. New York,USA:ASME Publication, 1995:99-105.
CHOI C, YOO H, OH J. Preparation and heat transfer properties of nanoparticle in transformer oil dispersions as advanced energy-efficient coolants [J]. Current Applied Physics, 2008,8(6):710-712.
SEGAL V, HJORTSBERG A, RABINOVICH A, et al. AC(60 Hz)and impulse breakdown strength of a colloidal fluid based on transformer oil and magnetite nanoparticles [C]∥Conference Record of the 1998 IEEE International Symposium on Electrical Insulation.Piscataway, NJ, USA: IEEE, 1998:619-622.
ZHOU Yuanxiang, WANG Yunshan,TIAN Jihuan, et al. Breakdown characteristics in transformer oil modified by nanoparticles [J]. High Voltage Engineering, 2010(5):1155-1159.
HWANG J G, ZAHN M, OSULLIVAN F M, et al. Effects of nanoparticle charging on streamer development in transformer oil-based nanofluids [J]. Journal of Applied Physics, 2010,107(1):014310-014317.
DU Yuefan, LÜ Yuzhen, LI Chengrong, et al. Effect of electron shallow trap on breakdown performance of transformer oil-based nanofluids [J]. Journal of Applied Physics, 2011,110(10):104104.
DU Yuefan, LÜ Yuzhen, LI Chengrong, et al. Effect of semiconductive nanoparticles on insulating performances of transformer oil [J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2012,19(3):770-776.
LIU Jun, ZHOU Lijun, WU Guangning. Dielectric frequency response of oil-paper composite insulation modified by nanoparticles [J]. Proceedings of the CSEE, 2011,31(28):144-153.
LI J, ZHANG Z, ZOU P, et al. Preparation of a vegetable oil-based nanofluid and investigation of its breakdown and dielectric properties [J]. IEEE Electrical Insulation Magazine, 2012,28(5):43-50.