Investigating the effects of oxidation and thermal degradation on electrical and chemical properties of power transformers insulation

This paper dcscribcs the analysis of thermally accelerated agcd insulation samplcs to investigate thc degradation processes observed in the insulation of aged transformers. Accaleratad ageing cxpcriments were performed on paper wrapped insulated conductors in the presencc of air and nitrogen environments over a tempcrature range of 115 to 145°C. Effects of oxidation on the ageing of oil-paper insulation were invcstigatcd and rcsults arc prcsentcd in I.his paper. The condition of agcd insulation samplcs was invcst,igatcd by a number of diagnostic techniques: (a)measuremcnts of interfacial polarization spectra by the rcturn voltagc method (b) measuremcnts nf molecular wciglit and its distribution hy go1 permeation chrornatography, (c) surface analysis by X-ray photo-electron spectroscopy and (d) a study of the oxidation of the oil by UV-visible spcctroscopy. Results from these measurements are prcsentad in this papcr and are uscd to analyse the degradation process with specinl emphasis on oxidation.