Estimation of Dielectric Parameters of Aged Natural Ester based Insulating Liquid using Open Beaker Oxidative Ageing technique

The conventional mineral oil (MO), which is used in the power and distribution transformers acts as an insulation and cooling agent. The insulation system in the high voltage apparatus, like the transformer, maintains the reliable functioning during its operational lifetime. However, the insulation system is stressed during the service and degrades in due course of time. Thus, alternate solutions to the conventional insulating system are being considered to augment the steadfastness of the transformer. The natural ester based insulating oils (NEOs) provides as a good substitute to the MO as it is biodegradable and has higher flash points and breakdown voltage. Moreover, with the addition of nanoparticles (NPs), the properties of the NEO are further enhanced. This paper provides a comparative study of some of the dielectric parameters of a natural ester-based insulating oil (NEO) and its nanofluids (NEO-NFs). The semi-conductive Titanium oxide (TiOz) NPs with a suitable weight percentage are dispersed in the base fluid to prepare the NFs. For the condition assessment of the oil samples, they are aged in an open beaker oxidative ageing (OBOA) apparatus for a duration of 500 hours to obtain the aged insulating liquids. This will help to assess the health of the oil after ageing for longer duration. A correlative study is carried out amongst the oil samples-NEO, NEO-NF, aged NEO and aged NEO-NF. It is observed that NEO-NFs performed better than the base fluid in terms of all its properties, both before and after ageing process. It is observed from the experiments that the NEO-NF with the semi- conductive TiOz NP shows substantial improvement in the dielectric properties.