ELECTRICAL AND CHEMICAL DIAGNOSTICS OF TRANSFORMERS INSULATION .A. AGED TRANSFORMER SAMPLES

This paper describes the application of two relatively new diagnostic techniques for the determination of insulation condition in aged trans formers. The techniques are (a) measurements of interfacial polarizati on spectra by a DC method and (b) measurements of molecular weight and its distribution by gel permeation chromatography. Several other elec trical properties of the cellulose polymer were also investigated. Sam ples were obtained from a retired power transformer and they were anal ysed by the developed techniques. Six distribution transformers were a lso tested with the interfacial polarization spectra measurement techn ique, and the molecular weight of paper/pressboard samples from these transformers were also measured by the gel permeation chromatography. The variation of the results through different locations in a power tr ansformer is discussed in this paper. The possible correlation between different measured properties was investigated and discussed in this paper.