Analysis Of Coupling Filed For GIL And Development Of The Monitoring System

Gas-insulated transmission lines play an irreplaceable role in UHV transmission,nuclear power,offshore large-scale wind power and other projects.The study of temperature field and thermal strain characteristics is of great significance for its safe and stable operation.The current research lacks the influence of temperature field and thermal strain characteristics,especially the ventilation speed under the laying of the pipe gallery,the solar radiation under the open layout and the different quantitative methods.It is impossible to accurately understand the mechanism of GIL temperature and thermal strain.And the law limits its application and development.Therefore,this paper uses multi-field coupling analysis method to study the temperature field distribution,thermal strain characteristics and influencing factors of GIL based on finite element software.Firstly,based on the theoretical calculation of electromagnetic field,the 550 kV GIL is taken as the research object,and the GIL simplified electromagnetic field model is established based on COMSOL software.The distribution characteristics of the single-phase GIL electric field and magnetic field in the sub-tank are studied.The electromagnetic heat loss of the GIL shell and the conductor under the rated working condition is calculated by theory and simulation,which provides a heat source for the subsequent flow-heat coupling and thermo-mechanical coupling analysis.Then the influence of gas convection heat dissipation on the GIL temperature field is taken into account,the corresponding assumptions and boundary conditions in the solution domain are given.The external air domain is loaded to establish the GIL flow thermal coupling temperature field model.The calculation of the three-dimensional steady-state temperature field of GIL is carried out without considering the ventilation and sunshine.The results show that the temperature has an axisymmetric distribution.Under the influence of natural convection of the internal insulating gas,the upper temperature is higher than the lower temperature and the extreme temperature of the shell appears at the top and bottom.The simulation model is used to study the influence of different operating environments on the thermal properties of GIL.It is found that under the influence of pumping speed and sunshine,the axisymmetric distribution of GIL temperature field is destroyed and the magnitude and position of the shell temperature are changed.There are some differences in the thermal properties of GIL.Then,in order to study the thermal stress and thermal deformation of GIL pipeline,the GIL thermal coupling method and process were analyzed.The coupled field of temperature field information calculated by COMSOL was used for GIL thermodynamic coupling analysis.Considering the convection of gas,analyze the thermal stress and thermal strain of GIL under the GIL rated condition.The research shows that the thermal strain and temperature field distribution are consistent.In order to study the influencing factors of GIL thermal strain,the quantitative analysis and comparison of GIL axial thermal expansion and contraction under different operating conditions were carried out.Finally,based on the GIL multi-physics coupling research,a set of GIL online monitoring system is designed according to the actual production needs,including SF6 gas condition monitoring,shell temperature rise monitoring,telescopic section variable monitoring,PD identification and positioning.