Insulation performance enhancement of aged current transformers using nanofluids

Abstract

The insulation performance of Current Transformers (CTs) is very important for their operational reliability. When the insulating oil in CT deteriorates, it has to be replaced by new oil, which is a costly solution. In this paper, a new technique for recovering insulating oil properties is proposed by using nanoparticles to form what is called nanofluids. For the first time, a real aged CT was used for the experimentation. Different insulation tests were carried out, breakdown voltage test on oil samples as well as dissipation factor, insulation resistance, and conduction current on the terminals of the CT itself. The aged insulating oil was first extracted from the aged CT, and then nanofluids were prepared by direct mixing of the oil with titanium oxide (TiO2) nanoparticles followed by ultrasonic processing for proper dispersion of nanoparticles. Different concentrations of nanoparticles were considered. After that, the CT was refilled with the prepared nanofluids. The experimental results either for the nanofluids or for the nanofluids-filled CT were compared to corresponding ones for the aged oil. The results indicated a great improvement in the breakdown voltage of the oil and in the insulation performance of the CT as a whole. Physical mechanisms behind the obtained results have been discussed.