Influence of Ageing on Properties of Insulating Oil in In-Service Transformer and Reactors

This paper aims at analysing the degradation in the properties of oil parameters such as breakdown voltage (BDV), interfacial Tension (IFT), resistivity, water content, dielectric loss tangent and total gas content due to ageing of transformer and reactors. For ensuring long term reliability of transformer and reactor it is necessary to ascertain the degradation characteristics of the insulating oil along with its impact on the healthiness of the equipment. The data considered comprises of real time oil test data of more than 500 samples of in-service transformer and reactors having age greater than 20 years. From the study BDV, IFT and Resistivity are found to be negatively correlated with ageing whereas water content, dielectric loss tangent and total gas content are found positively related with the ageing of equipments. The outcome of this study can be used as an effective index for monitoring the deteriorating characteristics of the oil filled transformer and reactor due to ageing.