Effect Of Grain Size And Twin Content On Sulfur Corrosion Resistance Of Copper Windings

Oil-immersed transformer,as one of the core equipment of power system,bears the functions of voltage transformation,power distribution and transmission.In recent years,the failure of transformer caused by oil-sulfur corrosion of copper windings has attracted wide attention at home and abroad.At present,most of the solutions to this phenomenon focus on insulating oil,such as strict acceptance of new oil,adding metal deactivator,and so on.In this paper,the effect of grain size and twin content on the resistance to oil and sulfur corrosion of copper windings is studied by adjusting the grain size and twin content in the copper windings through proper deformation and annealing process.At the same time,the mechanism of oil-sulfur corrosion resistance of copper windings,which is influenced by the size of crystal grains and the content of twins,is studied by means of chemical kinetics(electrochemical)and reaction thermodynamics.The main findings are as follows:(1)By adjusting the deformation and annealing conditions,two different series of copper windings are obtained.When the content of twinning is 20?23%,the grain sizes are 17.5?m,60.0?m and 133.0?m respectively;Copper windings with 18.2%,41.2%and 61.6% twinning at grain size are 18?22?m.(2)The corrosion resistance and mechanism of copper windings with different grain size were studied.It was found that the increase of grain size could improve the corrosion resistance of copper windings.The corrosion tendency and corrosion rate of copper windings were decreased with the increase of grain size measured by electrochemical workstation.From the thermodynamic analysis,it was found that the initial reaction temperature of copper winding with corrosive sulfur increased from107.8? to 121.1? with the increase of grain size.It was found that the activation energy increased from 9821.83J/mol to 15872.17J/mol with the increase of grain size.(3)The corrosion resistance and mechanism of copper windings with different twin content were studied.It was found that the increase of twin content could improve the corrosion resistance of copper windings.The corrosion tendency and corrosion rate of copper windings were decreased with the increase of twin content measured by electrochemical workstation.From the thermodynamic analysis,it was found that the initial reaction temperature of copper winding with corrosive sulfur increased from109.7? to 136.9? with the increase of twin content.It was found that the activation energy increased from 13790.35J/mol to 21918.70J/mol with the increase of twin content.The reaction temperature and activation energy between copper windings with different grain sizes and twin contents and corrosive sulfur were compared,increasing the twin content is more effective than increasing the grain size in improving the sulfur corrosion resistance.