Liquid kind, temperature, moisture, and ageing as an operating parameters conditioning reliability of transformer cooling system

The article presents research results of thermal properties of insulating liquids used in power transformer cooling system. The authors analyzed the influence of such factors, as the kind of the liquid, temperature, moisture and ageing rate of the liquid on thermal properties of the liquids. The analyzed properties of the liquids were thermal conductivity coefficient λ, kinematic viscosity υ, density ρ, specific heat cp, and thermal expansion factor β. These properties determine the ability of the liquid to heat transport – heat transfer factor α – what means the properties describe reliability of power transformer cooling system. The authors calculated the factor of heat transfer by the investigated insulating liquids on the basis of measured values of thermal properties.