Study On Temperature Characteristics Of 110kV Vehicle-mounted Mobile Transformer

In the case of electric power accidents,emergency repairs and natural disasters,vehiclemounted mobile substation has the advantages of convenient transportation,flexible and reliable,fast operation,which is of great significance to improve the reliability of power supply in power system.Vehicle-mounted mobile transformer is installed on vehicle platform as the core equipment of mobile substation,because of limitation of road transport conditions,conventional 110 k V transformer can not meet this requirement,therefore,it is necessary to reduce the quality of components such as windings and oil,to adjust radiator arrangement and cooling mode to reduce overall size,which will cause a great increase in load loss of mobile transformer and present a higher requirements of thermal performance,and high temperature will affect transformer damage and stability of power system operation when service life is serious.In this paper,the temperature field and heat dissipation performance of mobile transformer are studied.In this paper,aiming at a SFPZ-40000/110 ODAF oil-immersed vehicle mobile transformer,a 2-D axisymmetric transient model of single phase is established by using COMSOL software based on FEM,moreover,detailed structure of winding,insulating cylinder,baffle,guide are considered.Temperature variation curves of windings and top oil are analyzed when rated loss,rated current and power supply are applied to transformer short circuit method,and the overall temperature distribution nephogram at different time is obtained.The result will provide the foundation for the design of mobile transformer.Short-circuit temperature rise test is carried out for mobile transformer.Three-phase winding hotspots are measured by 8-channel optical fiber thermometer,and the temperature and temperature rise rate of oil tank wall,top oil and radiator inlet and outlet before and after transformer are measured by thermocouple thermometer.Comparing the simulation results with the experimental results,the maximum error is 3.6 C and the maximum relative error is 6.1%.,which verified reliability of the simulation.Moreover,comparing the calculated,simulated and measured values of windings with the empirical formula of oil average temperature rise,the maximum error is 12.7%.Futhermore,combining with field operation date,the winding temperature and top oil temperature curves under variable load are studied,and compared with the test curves,the results show that the curve fitting degree is higher when the load rate varies greatly and the load rate is low.We studied the effects of inlet temperature,load coefficient,inlet speed,winding baffle number and winding cake number on transformer temperature.The results show that the transformer is not suitable for long-term operation when the inlet temperature exceeds 65℃,load coefficient exceeds 1.1 or the inlet speed of the oil pump is less than 60% of the rated value.At same time,for winding structure,the number of baffles is between 5-9 and the number of wire cakes is between 55-65,which is conducive to reducing winding temperature and the power required by oil pump.In order to study the temperature field and heat dissipation of transformer air cooler,3-D simulation is carried out and the oil temperature difference between inlet and outlet of radiator and heat dissipation under rated loss are analyzed,at the same time,the results show that the error is 10.6% when compared with the theoretical calculation.In addition,based on the rated working conditions,we studied and analyzed the relationship between the oil temperature rise at the inlet of radiator,the oil temperature rise at the top and the radiator heat dissipation.We also analyzed the effects of wind speed,oil inlet velocity and oil inlet temperature on heat dissipation of cooler and oil temperature difference between inlet and outlet,and the convective heat transfer coefficient of air under different conditions.For the main structure of the cooler,the influence of heat pipe diameter,fin thickness and fin spacing on heat dissipation is analyzed.