Investigation of Natural Ester Insulating Fluid Properties and Thermal Model of a Transformer in Wide Temperature Range

Currently, a significant number of transformers are designed and used in the electricity distribution network. Since these machines are commonly based on an oil-paper electrical insulation system, it is crucial to know how certain important parameters of an oil behave within a wide range of ambient temperatures. Therefore, the range of temperatures should also include low temperature region as these conditions might occur in real application. The aim of this paper is to focus on the temperature dependent viscosity, density, thermal conductivity and specific heat of an oil in order to develop a strongly coupled thermal model of a transformer which is filled with biodegradable natural ester insulation fluid. Obtained results can be well applied within the design, operation and diagnostics phase of these types of electrical machines