Experimental Investigation of the Cooling Efficiency Impact Factors of Oil-immersed Transformer Split Cooling Systems

Abstract

Split cooling system is widely adopted for transformer cooling in underground HV and EHV substations in China. The cooling efficiency of oil-immersed transformer split cooling system is influenced by many factors, such as the cooling mode, the separated distance between transformer and the cooling installation, and the hoisting height of the cooling installation, etc. In this paper, typical cooling mode and split cooling installations in underground HV and EHV substations in Shanghai are investigated. For the investigation of the impacts of these factors on the cooling efficiency, cooling experiments are carried out with different layouts of split cooling installations on an 110kV/80MVA oil-immersed transformer and its split cooling system. The investigation and experimental results show that the cooling efficiency of the ODWF, OF/OF/AN and ONAN cooling modes decreases in turn. The horizontal distance between the transformer and the split cooling installation has little influence on the cooling efficiency, whilst the hoisting height of the cooling installation will significantly affect the cooling efficiency. Lifting the radiator will slow down the oil flow between the transformer and the radiator in the cooling system and thus reduce the cooling efficiency.