Fire Safety and Electrical Properties of Mixtures of Synthetic Ester/Mineral Oil and Synthetic Ester/Natural Ester

The paper presents research results of different properties of mixtures of the synthetic ester with mineral oil and synthetic ester with natural ester. For different concentrations of both mixtures, the following properties were investigated: flash point (open and closed cup), fire point (open cup), net calorific value, breakdown voltage, relative permittivity, dissipation factor, conductivity and dissipation factor. In order to compare results, prepared mixtures and base liquids were carefully arranged under uniform climatic conditions. This meant that the prepared samples had the same relative humidity. The obtained results were compared with the results of the base liquids. In addition, results of the investigation were analyzed in terms of fire safety and changes of electrical properties, in the context of the use of synthetic ester/mineral oil and synthetic ester/natural ester mixtures as insulation liquids in power transformers.