Impact of Aging By-Products on Moisture Estimation in Transformers using Dielectric Response Measurements

Abstract

Low and high molecular weight carboxylic acids (LMWA and HMWA, respectively) are polar organic compounds that appear in transformers as by-products of the aging of the oil and cellulosic materials. Due to its polar nature and easy absorption by the cellulose, the presence of LMWA in cellulose affects its dielectric frequency response (DFR) in a manner similar to the influence of water. As a result, the DFR moisture assessment on aged units with high amount of LMWA can be overestimated. The current paper presents a methodology for compensating the impact of the aforementioned aging by-products on the DFR-based moisture estimation in transformers.