| Compared to the500kV circuit, the transmission capacity and investment in1000kV circuit will improve several times. But it’s requirement of grid to the safe and stableoperation also increase. As transmission circuit directly support structure, safetyreliability of pole and tower structure directly related to the safety and reliability of thewhole state grid. The safety reliability should be how to select is an issue that is worthstudying.This paper’s mainly research work is as follows:①Reliability analysis on500kV transmission line that China has builtAbout pole and tower structure design for500kV circuit, our country hasaccumulated a wealth of experience in engineering design, and has formed a moresystematic pole and tower structure design codes. Researching structure reliability for500kV transmission line is significance of reference to the determine structurereliability for the1000kV UHV transmission tower. First of all, the reliability ofcalculation on500kV line tower structure of China in different periods is calibratedaccording to the current internationally accepted calculation of reliability. And throughthe investigation, this paper statistics the number of500kV transmission lines collapsed,through failure frequency of the500kV transmission circuit launched its theapproximate scope of the failure probability.AndThen the proposal on the setting ofreliability level of1000kV UHV transmission tower is raised.②Design method and reliability index of1000kV UHVThe domestic and international representative standards of tower design and loadare collected, including IEC standard, the United States guideline and European Unionstandard. Through a series of derivation, comprehensive reliability coefficient of eachstandard is found out. By comparing the comprehensive safety coefficient, theconclusion about the quantitative ratio of the reliability level of standards home andabroad is drawn. Based on this, several conclusions are proposed including the designmethod, load condition and load combination, the setting of reliability level of ourcountry1000kV UHV transmission tower structure, structure importance coefficient,return period of wind load, etc.③The reliability analysis of1000kV UHV transmission tower system based onthe moment methods The equivalent static wind load model is used, which considers the randomness ofaverage wind pressure and the random process of pulse wind pressure and the stochasticdynamic effect on structure. The reliability of structure under the actual wind load andthe reliability of structure under the equivalent random static wind load which iscalculated by the static reliability analysis can be considered to be equivalent. Byintroducing equivalent extreme-value event, the reliability of structure is simplified asseries system of each failure mode and corresponding equivalent extreme variablequantity is proposed. Then, point estimate method is used to solve statistical moment ofequivalent extreme variable quantity and according to the statistical momentinformation four order moment method is used to solve the reliability index and failureprobability of the structure system. The research of1000kV UHV transmission towersystem shows that①the moment method is simple and efficient;②the windreliability analysis of UHV transmission tower system based on the equivalent staticwind load model is feasible and has important theoretical significance and engineeringpractical value;③it can spread to apply in the reliability analysis of practical projects.④1000kV AC UHV full-scale tower test and finite element simulationThrough the finite element simulation analysis of1000kV AC UHV full-scaletower test, the secondary stress influence method is put forward, verify the local yieldtest results are verified, the reliability of this study is showed.Finally, on the basis of summarizing the full text further research prospect isproposed. |
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