Dynamic behaviour of sub- m particles in dielectric liquids under DC stress

Nanofluids (NF) are produced by dispersing nanoparticles into the host liquid, such NFs are currently under investigation by different research groups as they can offer improvement in both the dielectric strength and thermal conductivity compared with traditional insulating liquids. In this paper, the Maxwell-Wagner relaxation process theory was employed to investigate the dielectric response of particles suspended in insulating liquids to a step voltage. The experimental part of the paper was focused on measurements of the conduction current through pure liquids and NFs, these measurements were combined with the monitoring of the particle dynamics using a video camera and optical microscope. Thus, investigation of the behaviour of nanoparticles (TiO2 and BN) dispersed in synthetic esters and in mineral oil has been studied under DC stress over long time intervals (up to 60-mins). The obtained results demonstrate that the dynamic behaviour of the nanoparticles is strongly affected, not only by their dielectric permittivity and electrical conductivity, but also by the host liquids’ dielectric permittivity and electrical conductivity. This work will help in the development of new NFs for practical applications in the power and pulsed power industries.