Nanoparticle Effect on Dielectric Breakdown Strength of Transformer Oil-Based Nanofluids

Different types of nanoparticles with various electrical conductivities were used to modifying the mineral oil. AC and lighting impulse breakdown voltages of the three types of nanofluids and the pure oil were tested according to the IEC standards. All the nanofluids possess higher dielectric property than pure oil. Possible mechanisms to explain the enhancement of dielectric strength of nanofluids are discussed. Conductive nanoparticles with extremely low charge relaxation time constant in the transformer oil could capture the fast electrons and convert them into low mobility negatively charged nanoparticles. Conductive nanoparticles act as electron scavenging in the fluid. Adding semi-conductive nanoparticles and insulating nanoparticles can both produce shallower traps in the oil. It is proposed that electron trapping and de-trapping processes in the shallow traps could be main mechanism in these nanofluids.