Survey On Research And Practice Of UHV Transmission Technology

Nowadays, the distribution of energy resource and load determine that we have to construct long distance, great capability UHV transmission line. Thereby, the problem that must be solved in the development of UHV is to strengthen the research of UHV transmission system.Firstly, based on the differences of technical and economic characteristics of UHVAC/UHVDC, their applications in China are compared in the paper. Then, some important technical problems of UHVAC/UHVDC, such as reliability, stability, electromagnetic environment of power grid and DC/AC coordination are discussed and compared.Secondly, for improving the lightning performance of UHV transmission line, the paper proposes the calculating model of lightning strike width of transmission line which is based on the striking distance theory. With such model, the back striking trip-out rate of transmission line is calculated. Then based on both EMTP method and EGM method, the lightning withstand performances of back striking, shielding failure for UHV transmission line are analyzed. Research results show that the shielding failure is the main reason for lightning striking tripping of UHV transmission lines. Because UHVDC transmission line exists polarity problem, the critical current required for flashover of negative line is far higher than that of positive line.Finally, the current status of equipments manufacture of UHV transmission project, especially the establishment of UHV test base, has been introduced in this paper. Then some technical problems of UHV system, such as over-voltage and insulation coordination, high-low voltage electromagnetic, AC-DC hybrid operation, are discussed.