Analysis and Diagnostic of Distribution Transformer Oil in Lieu of Life Expectancy

Abstract

All over the worldmineral oil immersed transformers play an important role in generation and transmission of electric power. Mineral based insulation oil is used for liquid insulations in transformers for the past some decades. During their service life thermal, mechanical and electrical faults usually occur in transformer due to local overheating, hot spot, leakage flux, arcing, eddy current etc. These faults largely affect the liquid insulation resulting in production of unique degraded products that are present in transformer oil permanently or for a considerably short period. Presence of these products in the oil changes its basic property and increases the aging process of transformer oil.This paper presents the experimental results of effect of aging of transformer and analysis the change in characteristics such as density, viscosity, dielectric strength or breakdown voltage, flash point and fire point of the mineral based transformer oil with aging and X-Rayfluorescence(XRF) test is carried out for analysis of presence of corrosive sulphur in pure and used oils. The presence of corrosive sulphur in the oilaffect the copper windings and may form copper sulphide which deposits on oil-paper insulation system which can lead to insulation failures in power transformers.

Keywords: viscosity;breakdown voltage; flash point; fire point;XRF; mineral oil