Review of Cooling Methods for Oil-Immersed Transformers

With the growing demands for electricity, the safe and stable operation of transformers are crucial. Oil-immersed transformers are widely used in power systems due to their excellent heat dissipation and insulation properties. However, the traditional oil-immersed transformer cooling methods are difficult to meet the needs of modern power systems, therefore, new cooling methods need to be developed. The existing oil-immersed transformer cooling methods are varied, including oil natural air natural (ONAN), oil-natural air-forced (ONAF), oil-forced water-forced (OFWF), oil-forced air-forced (OFAF), oil-direct air-forced (ODAF), oil-direct water-forced (ODWF) and natural oil circulation cooling method with directed structure, each of which has its own advantages and disadvantages and is applicable to different scopes. In addition, the choice of cooling medium also has an important impact on the cooling effect of the transformer, mineral oil, natural esters, synthetic esters and other different medium have different properties. This review introduces the medium, principles and practical application of oil-immersed transformer cooling methods, aiming to help power system engineers and technicians have an in-depth understanding of the oil-immersed transformer cooling methods and provide references for them to select suitable cooling methods and optimize transformer cooling systems. Moreover, this review also provides certain theoretical basis and ideas for the research and development of transformer cooling methods, promotes the progress of transformer cooling methods and provides more reliable guarantee for the safe and stable operation of the power system.