Analysis of thermal processes in a special oil-immersed power transformer

When modernizing power electrical equipment, it is essential to assess its thermal condition in various operating modes. The accuracy of determining temperature parameters significantly affects the lifespan and reliability of the new device, as well as allows for an assessment of the correctness of the selection of electromagnetic loads in the active parts. The article addresses the issue of assessing the thermal state of a specially designed power oil transformer, which, alongside the magnetic core and power windings, features a heat exchange unit that allows for the utilization of part of the transformer's losses to heat the heat transfer fluid. The described design of such a transformer includes a tubular type heat exchange unit. The main thermal flows have been analysed, and equivalent thermal replacement schemes of the active part have been provided, taking into account the heat exchange unit, along with a simplified thermal scheme of the entire transformer. The need for precise determination of thermal resistances in the path of heat flow from transformer oil to the heated heat transfer fluid has been identified. For this purpose, a field problem was solved using the finite element method in the Flow Simulation module of the SolidWorks computer-aided design software. The results of computer modeling for various parameters of the heat carrier have provided recommendations for determining the desired thermal resistances for different operating modes of heat exchange equipment in the design of special-purpose power transformers.