Thermal Performance Assessment of Power Transformer Winding Through Experimental, Analytical and Numerical Analysis

The loading and life expectancy of power transformers are ruled by the high internal temperatures. Predicting the temperature distribution and hotspot locations during the design stages is fundamental to reliable equipment. Once in operation, online monitoring of these temperatures through a measurement system is of great importance to ensure its safe operation and the power system reliability. This paper presents the thermal evaluation of a step-up 230 kV power transformer, filled with natural ester insulation oil. Its thermal performance is assessed through optical fiber sensors measurements along the active part during the heat run test. The punctual experimental results are compared to complete analytical calculations from a thermal-hydraulic network model, which solves the oil flow and temperature distribution fields. CFD simulations are performed to assist the analysis, allowing visualization of the oil flow and temperature distributions with details along the oil channels, considering the mechanical arrangement. Therefore, contributions to the transformer industry in relation to thermal design and optical fiber monitoring are made, considering the constructive arrangement and the use of numerical and analytical tools to improve the equipment efficiency.