Enhancing flashover strength along oil/pressboard interface using nanofluids

One of the weakest paths for electrical discharge in power transformers is oil/pressboard interface. So, in this study it is aimed to enhance the flashover resistance of such interface through using the concept of nanofluids. Nanofluid impregnated pressboard were prepared using two different types of nanoparticles. These types are Alumina (Al2O3) and Titania (TiO2) which have different values of zeta (ζ) potential that had been experimentally measured. Flashover tests are carried out at pressboard interface with nanofluids and mineral oil. Three conditions of oil flow are considered, static and turbulent dynamic flow with two different circulating velocities. Flashover strength of nanofluid impregnated pressboard was tested for different weight fractions of nanoparticles and was compared to that of the base mineral oil. In each test, the value and polarity of applied AC voltage at the instant of flashover was recorded. Weibull distribution was used for analyzing flashover strength data. The polarity at which flashover occurred was positive in all tests. Physical mechanisms have been discussed considering electron trapping and double layer model of nanoparticles.