Mechanics Analysis Of Electric Power Crossing Frame In UHV Engineering

China is a world leader in Ultra High Voltage(UHV)transmission engineering.UHV project has the characteristics of large transmission capacity,long transmission distance,small transportation loss and small footprint.UHV is recognized as an important way of realizing the alloca tion of power resources and enhancing the transmission capacity of power grid in our country.Transmission line constructions usually need to cross the already built power grid,high speed railways,expressways and other important facilities.In order to ensure the safe operation of these facilities,the network protection measures need to be taken.In this paper,the crossing technology has been combed and analyzed.The forms of crossing frames suitable for different types of obstacles are summarized.The mechanics model of crossing frame is established for the numerical simulation analysis.The influences of layout of scissor support,the construction form(pole spacing,large bar spacing,small crossbar vertical and horizontal spacing,row spacing,etc.),the height and row number of the crossing frame are investigated.The results show that the structural parameters have a significant effect on the mechanical properties of the crossing frame.Compared with the crossing frame stalling scissor support only on the outer surface,the structure with scissor brace on small cross-sectional elevation has smaller lateral displacement and higher stability.It is recommended that the scaffold should use scissor brace on the small cross-sectional elevation in practical engineering.As the height increases,the overall displacement intends to rapidly increase,and the stability evidently reduces.Moreover,the stability decreases sharply with the increase of the bearing load of the crossing frame.In addition,increasin g the number of rows of the frame is helpful to reduce the stress and displacement of the structure and improve its stability.The dynamic response of the crossing frame under the impact of the wire is analyzed.The results exhibit that the simplified mode l of the three-span continuous beam is more accurate to reflect the dynamic response of the component of crossing frame under the impact than the model of simply supported beam.When the wire strikes the frame,the instantaneous displacement and stress amplitude of the frame increases linearly with the increase of the mass of the impact,and the vibration time is longer and the fluctuation is larger.The higher the drop height of the wire is,the greater the energy contained in the conductor is,and thus th e greater the displacement and stress caused by impact are.Dynamic response is different caused by impact in different position.The coupling model of the crossing frame and the insulation net is constructed.The influences of the height of the frame,the form of the net,the position of the load on the insulation net and the height difference between the two sides are investigated.The results show that the deformation of the insulation net is beneficial to reduce the direct impact effect of the wire drop on the crossing frame,and effectively disperse the position of the wire load on the frame,which benefits to improve the safety of the crossing frame.The form of insulation network layout influences the sag of carrying rope and changes the angle between the frame and carrying rope,which causes the load direction on the crossing frame be changed.But the effect is very small when the span distance is not too far.The displacement and stress of the higher side of the frame is less affected by the height d ifference between the two sides of the frame,but the influence of the height difference on the lower frame is relatively large.