Optimization of Sulphur Hexafluoride Bubbling Cooling System for Oil Immersed Power Transformer
Abstract
The article proposes a computational and experimental method for optimizing the operation of a gasinsulated bubbling cooling system for an oil transformer under variable electrical load. The problem is formulated as minimizing the energy consumption of the gas circulation circuit while simultaneously adhering to constraints on the winding's hottest point temperature, oil temperature, volumetric gas content, and closed-loop pressure. A reduced thermal model of the transformer, whose parameters are identified based on bench test data, is used to solve the problem. The control action is determined by the SF6 gas flow rate through a porous bubbler, and optimization is performed over a forecast horizon with an additional uncertain correction for the temperature rise rate. It has been shown that the main heat transfer intensification effect is achieved in the moderate flow rate range, where the bubble layer disrupts the wall thermal layer and enhances oil mixing without exceeding dielectric and hydraulic limits. The obtained results confirm the possibility of reducing the temperature of the hottest point and reducing energy consumption for auxiliary needs compared to a continuous gas supply mode.