Investigation of Transformer Oil Aging Under Service Load from Various Dielectric Measurements, Chemical Analysis and Spectroscopy PDF

Keywords

transformers, oil, temperature

Abstract

This work presents the experimental results of the effect of field strength and temperature on the dielectric and physical properties of transformer oil sampled from EHV transformer operating for the past seven years. Aged oil was compared with fresh transformer oil and the impact of filtration and degassing on the dielectric, and physical properties are discussed. Viscosity, relative humidity and cations content are correlated with dielectric properties. Experimental studies reveal that dielectric loss index for all samples is field independent but temperature dependent and increases exponentially as the temperature is increased. Dielectric loss index provides a reliable picture of oil aging as its value increases rapidly with the age of oil. Ferric iron content is increased by large factor due to aging. Carbonyl groups and polar products could not be detected in the oil samples using GC, JR, PMR and 13C-NMR techniques of spectroscopy.