Investigations on detectability of different acids in paper-oil insulation

Abstract

Transformers are key elements in power generation and distribution. A large part of the world's transformer fleet is older than its intended service life. The risk of transformer failure increases with age, with the oil-paper insulation of the windings being a major cause of transformer failures. It is mainly the large expensive power transformers that have oil-paper insulation. During the service life of a transformer, its paper-oil insulation is exposed to mechanical and thermal stresses that initiate the aging and degradation process of the insulation. In the course of degradation, both high- and low-molecular weight acids (HMA and LMA) are formed. These acids change the physicochemical properties of the insulating oil and in turn, cause the paper to decay. The LMAs in particular are known to be responsible for paper aging, as they initiate chain scission of cellulose molecules and remain in the paper. In this article spectroscopic examinations of low-molecular weight acids, laboratory-aged paper samples, and unaged acid-injected paper samples are conducted, to determine whether different concentrations of acids in paper samples can be detected using IR-spectroscopy.