Statistical Analysis of Partial Discharge, Lightning Impulse and BDV Characteristics of Nano SiO2-Corn Oil for HV Insulation Applications

Abstract

Recent concern towards environmental and fire safety of transformer operation has led to the development of natural ester based liquid insulation for power transformers. Recent advancements in nano technology confirm that the nano modified liquid insulation provides superior dielectric and thermal properties. Statistical analysis of the dielectric properties of nano modified liquid dielectrics is very important to qualify them for high voltage insulation applications. In this work, experimental works are carried out to understand the partial discharge (PD), lightning impulse (LI) and breakdown voltage (BDV) characteristics of corn oil filled with SiO2 nano fillers at different wt% concentration such as 0.01%, 0.05% and 0.1%. Needle/plane and rod/plane electrode geometry was used for creation of PD source. PD inception voltage, time domain and frequency domain characteristics of PD signals are evaluated. Weibull parameters of Phase Resolved PD pattern are evaluated. LI tests are performed at needle/plane and needle/sphere electrode geometry with standard 1.2/50 µs waveform at both positive and negative polarity. Weibull distribution analysis of LI breakdown voltage values are evaluated at different experimental conditions. BDV tests are carried out at different electrode gap distances such as 1, 2.5, 4 and 5 mm. Scale parameter and shape parameter of Weibull distribution of BDV values are computed. It is mostly observed that addition of nano SiO2 filler at lower wt% concentration in the range of 0.01–0.05% has substantial effect in enhancing the PD, LI and BDV characteristics of corn oil. Improvement in PD, LI and BDV characteristics gives confident that nano modified corn oil may be considered for outdoor transformer applications.