| Ice storm is the most serious menace to power grid, it has endangered the 500kV lines even the 1000kV lines shown by operational experiences. After the ice-storm of 2008, short-circuit-current ice-melting (SCCIM) is accepted as the effective method to resist ice storm of power grid by the State Grid Corporation and the Southern Power Grid Company, and a lot of human, financial and material resources are put into the research and development of the methods and equipments for the SCCIM. One of the key problems is to estimate the ice-melting current according to the ambient conditions and the icing status when SCCIM is applied to transmission line. However, it has not been deep research at home and aboard up to now.According to the icing characteristic of Chinese power grid, based on the analysis of ice-melting mechanism, this paper has put forward a physical and mathematic model for SCCIM, and has analyzed its factors including wind velocity, ambient temperature and icing status. The simulated results have been investigated both in the artificial climate chamber and the field icing experimental station.In this paper, the cross-section shape of icing conductor has been characterized with ellipse according to the practical characteristic of ice on transmission line in the natural environment, and the critical conditions of SCCIM, namely the inner temperature of ice-layer kept 0°C and the joule heat is equal to the heat loss on the outer surface of ice-layer has been analyzed. Then, the factors of critical ice-melting have been investigated and the calculation method for critical ice-melting current on various environmental parameters has been submitted.The ice-melting physical process of transmission line has been analyzed and a physical and mathematic model of SCCIM for elliptic icing conductor has been built. By the finite element and the finite difference method, the ice-melting phase change problem (Stefan problem) of elliptic icing conductor has been solved and the calculation method for the SCCIM model has been submitted. And then, the dynamic varying process of the temperature of ice-melting conductor has been simulated, and the calculation methods for ice-melting time, ice-melting current and the maximal temperature of ice-melting conductor have been raised.The factors to influence SCCIM of elliptic icing conductor have been analyzed. The results show that wind velocity, ambient temperature and ice thickness are of obvious effect to the SCCIM of elliptic icing conductor, furthermore, the icing conductor shape influences the ice-melting time. When the ice mass on conductor is changeless, the ice-melting time varies with the icing eccentricity on the opposite direction, and it reaches its minimum when the icing eccentricity reaches its maximum, namely the cross-section shape of icing conductor is circular.Many ice-melting experiments in the artificial climate chamber and the field icing experimental station have manifested that the simulated results were approximatively consistent with the experimental ones, and the simulated ice-melting process was similar with the experimental one. In addition, the non-simultaneous ice-shedding phenomenon has been investigated in the field icing experimental station. Both the experimental results and the theoretical ones show that the ice sheds from the conductor non-simultaneously due to the difference of icing thickness and climate parameters along the conductor.The ice-melting effect of AC SCCIM is same with that of DC SCCIM in essence when the root mean square of AC is equal to the DC. But the ice-melting time of large cross-section conductor is less than that of the small cross-section conductor for the AC skin effect. However, the power capacity of AC ice-melting is much greater than that of DC ice-melting because of the line inductance.This research have focused on the ice-melting process of elliptic glaze icing, not including the other shapes and other icing types which were of influence to the ice-melting and would be studied in the future.
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