An Experimental Study On The Influence Of Surface Modification Of Tio2 Nanoparticles On Breakdown Voltage Of Natural Ester Nanofluid

Insulating oils are widely used as dielectric liquid in power transformers because of their high electrical strength and cooling properties. The last decades a technique that is used in order to improve both the dielectric and thermal properties of dielectric liquids is the synthesis of nanofluids by integration of nanoparticles in insulating oils. In several cases, surfactants are also added to the nanofluids modifying the surface of the nanoparticles in order to reduce the agglomeration inside the oil. In this paper, the nanofluid samples were prepared by integration of TiO2 nanoparticles using the two-step method, while the addition of the surfactant Sorbitan Monolaurate aims to enhance the dispersion of the nanoparticles. AC breakdown voltage characteristics of the surface modified nanofluid samples were measured according to IEC 60156:1995 standard methods in specific TiO2 concentrations according to our previous work, where TiO2 nanoparticles had been added into FR3 without the surface modification. Normal and Weibull distributions were used to calculate the breakdown probability for the surface modified nanofluid samples. The results showed that there is an improvement in terms of the mean breakdown voltage and sedimentation has been delayed significantly compared to the ones without surface modification. Breakdown voltages at 10% and 50% were calculated after the fitting of the results to Normal and Weibull distributions. Enhanced AC breakdown voltage at 10% probability is an indication of the increased reliability of the nanofluid. On the other hand, breakdown probability at 50% is an indication to the mean breakdown voltage.