Ratings of Oil Power Transformer in Different Cooling Modes

This case study shows the application of the calculation method based on the detailed thermal-hydraulic network model. The method is applied for the thermal design of oil power transformer of rated power 750 MVA in oil-directed, air-forced cooling mode; rated powers are also specified for oil-natural, air-forced and oil-natural, air-natural cooling modes. The results of the calculations using developed software for three cooling modes are compared with the results of the heat-run test of the transformer equipped with fiber-optic sensors. In addition to confirmation of the accuracy of the model, this paper demonstrates the full power of the integrated method (inner heating and outer cooling) for thermal calculations. All relevant components (pressure drops, oil flows, oil temperatures, etc.) in different cooling modes are obtained from the model and exposed in this paper.