Influence of transformer oil decay products on its thermal conductivity

The fluid inside transformer must function as an insulating medium and heat transfer agent. During service, there is a gradual deterioration of the fluid that eventually compromises the unit’s reliability. In this contribution, the physicochemical and thermal properties of aged oil are studied. It is shown that with the production of oxidative aging by-products, the physicochemical properties along with the thermal conductivity and viscosity of oil are affected. From the obtained results, it seems that the decay products increase slightly the thermal conductivity of oil. The cinematic viscosity as aging time progressed may be directly correlated to the turbidity and dissolved decay products results. Measuring the amount of insoluble/soluble suspensions therefore appears to be very important, since these by-products clearly affect the insulating oil physicochemical properties.