Dielectric Properties and Fire Safety of Mineral Oil and Low-Viscosity Natural Ester Mixtures in Various Concentrations

Abstract

This paper presents the results of testing the electrical and fire properties of mineral oil and low-viscosity natural ester mixtures. Properties such as breakdown voltage, relative permeability, dispersion coefficient, conductivity, flash and burn point, and lower heating values were investigated in different concentrations of mixtures of the two liquids, as well as for the base liquids. To ensure equal humidity levels, the prepared samples of mixtures and base liquids were conditioned under identical climatic conditions, resulting in samples with similar relative humidity (9 ± 3)%. The obtained measurement results for mixtures of the two fluids were related to the values obtained for the base liquids and analyzed in terms of changes in electrical properties and fire safety when used as insulating liquids in transformers. The presented results are useful for supplementing knowledge on the possibilities of using dielectric liquid mixtures in high-voltage power devices, with to the aim of using mixtures as alternatives to mineral oil.

Design and Optimization of Power Transformer Diagnostics

“…This is due to their different structure and therefore other properties, for example, dielectric properties or the ability to exchange heat in a transformer. Below, we discuss issues related to fire protection [1], electrical [2], thermal [3], and gassing properties [4], the streaming electrification phenomenon [5], moisture [6,7], and the degradation of cellulose fibers [8] working with alternative liquids and their mixtures with mineral oil. Dombek and Gielniak, in [1], investigated the influence of the proportion of mixing mineral oil with natural ester with reduced viscosity on selected dielectric and fire properties.…”

“…Below, we discuss issues related to fire protection [1], electrical [2], thermal [3], and gassing properties [4], the streaming electrification phenomenon [5], moisture [6,7], and the degradation of cellulose fibers [8] working with alternative liquids and their mixtures with mineral oil. Dombek and Gielniak, in [1], investigated the influence of the proportion of mixing mineral oil with natural ester with reduced viscosity on selected dielectric and fire properties. It was shown that mixing the two liquids can contribute to an increase in the flash point and burning of the resulting mixture, relative to the mineral oil.…”

“…Most articles in this Special Issue, as many as eight, are devoted to issues related to alternative liquids [1][2][3][4][5][6][7][8], such as natural esters and synthetic esters. However, there are also five papers devoted to the methods of measuring partial discharges [9][10][11][12][13], and one article each is devoted to the following subjects: the determination of dielectric losses in transformers [14], the design of the dry suppressor core [15], the estimation of the transformer health index [16], and the working conditions of fitters carrying out diagnostic measurements [17].…”