Influence of the titania nanoparticles and surfactant in the mixture of mineral oil and rapeseed oil used in the transformers

Abstract

The Mixture of mineral and ester oil in transformers is gaining popularity in retro-filling mainly due to the high biodegradability and excellent thermal and dielectric properties of ester oil. Mixed oil-based nanofluid holds a high potential to improve the insulation properties of a liquid dielectric. In the current study, the effect of Titanium oxide (Titanium oxide (TiO2) ) on dielectric properties of an optimum mixture of ester and mineral oil has been studied. Based on the Corona Inception Voltage (CIV) and Breakdown Voltage (BDV) under AC, DC and Lightning Impulse (LI) voltage application, an attempt has been made to optimize the percentage of nanoparticles for attaining superior dielectric properties. Similar methods are employed to optimize surfactant ratio (Cetyl Trimethyl Ammonium Bromide (CTAB) and Oleic Acid (OA)) in a nanofluid. It was observed that with needle plane configuration, negative DC voltages have high breakdown voltage as compared to positive DC and AC voltages. Incipient discharges are observed to emit electromagnetic radiations of Ultra High Frequency (UHF) range signal with a dominant frequency near 1 GHz. The magnitude of discharges formed in nanofluid with CTAB is much lower than pure mixed oil in Phase Resolved Partial Discharge (PRPD) analysis. It is observed that compared to pure ester oil, loss tangent and permittivity of mixed oil-based nanofluid are improved and can thus be proposed as an optimal replacement for transformer insulation. newline