Evaluation of the Properties of Mixtures of Aromatic Mineral Oil and Synthetic Ester for High-Voltage Equipment

Abstract

This article discusses the possibility of enhancing the insulating characteristics of a mineral oil-based on petroleum with high aromatic hydrocarbon content (23%) by mixing it with the synthetic ester Midel 7131. An assessment of the insulating properties of mixtures with ester content in mineral oil from 0 to 100% is given. The main characteristics of mixtures are described, such as density, kinematic viscosity, flash point, dielectric loss tangent, relative permittivity, breakdown voltage, moisture content and oxidation stability. It is shown that with an increase in the proportion of ester, some parameters of the obtained insulating liquid improve (flash point, relative permittivity, breakdown voltage, oxidation stability, corrosive sulfur), while other parameters (density, kinematic viscosity, dielectric dissipation factor) change to invalid values. Unlike a mixture of pure unused mineral oil with ester, the addition of unused synthetic ester to used high aromatic mineral oil (taken from a transformer in operation) results in an abnormal increase in the dielectric dissipation factor.