Research Of The Wear Performance On The UHV Transmission Line U-rings And Adjusting Rings

Recently years, UHV transmission lines rapidly developing in China and the votage class getting higher and higher. But the wear resistance of U-rings and the adjusting rings which connected directly with the transmission lines and insulators will influence the safety of operation. Overhead transmission lines tend to vibrate because of the wind. Friction between fittings themselves or wire and fittings will break the zinc coating at fittings surface, and will reduce the life of the fittings. This paper is based on the research project of Yunnan Electric Power Research Institute. Tested the wear resistance of U-ring and adjusting ring as to study the discipline of the fitting abrasive. Finite element method(FEM) is also used in this paper. Accomplished main task as followed:(1) Fitting wear performance is tested with the experiment. This paper tested U-rings and adjusting rings on the wear performance under the load. Simulated U-rings and adjusting rings related motion under the working condition. Electron microscope is used to watch the part of fitting wear. Then, use the method of spectrum to see the surface morphology characteristic, as well as the scanning electron microscopy(SEM) to wear debris. As a result, at the bottom of U-rings curved edge, tiny crackles which hard to see by the naked eye exist as the length of 1111.67μm. Those crackles will exacerbate the erosion and strain concentrate that will result in an accident. SEM result of the wear debris shows that gully of curved edge is match to the wear debris. After energy spectrum analysis, confirmed that black powder debris is the oxide of zinc coating and steel of the fittings.(2) Two statistical methods of fittings for wear were raised. One is the variation of zinc coating thickness detection method. Use the coat thickness measure instrument to measure fittings before and after the test to find out the law of wear. It is a simple and effective way to accounting the wear. The other is method of mass variation with subtraction. That means weigh the fittings before wear test and after wear test, it’s a directly way to accounting the wear. The result shows that, variation of zinc coat thickness detection method has its own limitations. If the zinc coat were all consumed after the wear test, statistic deviations will emerge according to the measuring principle. However, data that measured by method of mass variation with subtraction is rough. Thus, this paper comprehended two methods to measure U-rings and the adjusting rings not only ensured data completion, but also raised the precision of data.(3) The application of ANSYS finite element method to simulate the U-ring contacted position with adjusting ring. Impose 100 kN loads onto sample to get the whole stress distribution. With the time step is 0.1, the maximum stress appeared at the link of U-ring and adjusting ring which reached 403 MPa. With the time step is 0.6, the maximum stress appeared at the area of bolt hole in U-ring and adjusting ring which reached 557 MPa. Calculated the stress of wear area and simulated the surface topography and contact slippage. Contacted stress up to 840 MPa and the slippage of U-ring and adjusting ring curved edge is 1mm. Result shows that U-ring and adjusting ring contacted curved edge have the most contact stress. Meanwhile, the strength of bolt linked part is supposed to be attached to the importance.This paper raised the method of the fitting’s wear performance, provided experiment and theory basis of the simulation of UHV transmission lines’ fitting wear performance. Experiments and FEM method are used to U-rings and adjusting rings which are common used in transmission lines. The paper improved theoretical and practical significance of U-ring and adjustment ring due to wear decrease the fatigue life. Follow-up work of fitting wear performance by the experiment established theoretical and practical basis.