Research On On-line Monitoring Method Of GIS Structure Displacement In Large Substation Based On Finite Element Analysis

Gas Insulator Switchgear?GIS?has been widely used in many substations at home and abroad because of its safety,reliability,easy maintenance and small footprint.However,due to errors in design,manufacturing,and installation,as well as harsh operating conditions and environmental factors,GIS equipment may undergo displacement or deformation due to temperature changes due to temperature changes,such as thermal expansion and contraction or foundation subsidence,equipment vibration,etc.These deformations and local stresses will lead to failures such as cracking of the GIS equipment cylinder,support fracture,SF₆ gas leakage,and ground discharge.In this paper,the GIS equipment of a 500kV substation was taken as the research object.The finite element analysis of its structure was carried out by ANSYS software.The main monitoring parameters and program requirements of online monitoring of GIS equipment status were discussed based on the results of finite element analysis,and the on-site layout of the hardware of the non-contact displacement online monitoring technology was guided.Firstly,the overall structure of the GIS equipment was divided into four key parts to establish a finite element analysis model,including tube busbar+fixed support,tube busbar+sliding support,self-balancing bellows expansion joint,and ordinary bellows expansion joint.The stiffness calculation of the bellows expansion joint was carried out by unit selection,modularization and parametric modeling and determination of boundary conditions.In the subsequent overall model,a self-balancing bellows expansion joint could be used with a nonlinear spring unit COMBIN39,the spring stiffness was divided into three sections;a linear spring unit COMBIN40 with a stiffness value of 322310 N/mm could be generated instead of the ordinary bellows expansion joint.The key parts were combined to establish a GIS equipment overall model,and the finite element analysis of GIS equipment under extreme temperature conditions in summer and winter was carried out.The analysis results show that the maximum displacement of the GIS equipment in the 500kV substation appeared near the pressure self-balancing bellows expansion joint,and the maximum displacement occurs at-5 to 70°C,which is 42.29 mm.In the case of the temperature difference of the installation condition of 35⁷0°C and the temperature difference of-5^-20°C,the structural stress is within the allowable stress range,and the structure is safe and reliable.However,in the temperature difference of 35^-20°C and the temperature difference of-5⁷0°C,the joint of the busbar and the bellows expansion joint in the GIS equipment may have stress concentration phenomenon and yield.When operating under conditions of large temperature difference,the busbar of GIS equipment is more likely to cause leakage problems due to yield deformation.By comparing the actual monitoring data of the substation GIS equipment with the result data of the finite element analysis,the two data are basically consistent,and the displacement change trend is the same.The corresponding analysis of the GIS equipment structure can be carried out according to the model.According to the finite element analysis results of GIS equipment and the actual situation of the site,the specific requirements of the monitoring scheme of the structural state during the operation of GIS equipment was proposed.The main parameters of GIS equipment monitoring:displacement,temperature,wind direction,wind speed and other basic measurement methods,measurement range and accuracy requirements wre discussed.The system scheme of real-time monitoring of GIS equipment was designed.According to the actual situation of the GIS equipment of a 500kV substation and the finite element simulation results,the installation position,installation method and quantity of the displacement sensor,temperature sensor,wind direction sensor and wind speed sensor were determined.The preliminary displacement monitoring data obtained from the monitoring scheme were compared with the simulation data to verify the feasibility of the design scheme.