R&D progress of ±1100kV UHVDC technology

The successful construction and reliable operation of Xiangjiaba-Shanghai project fully proved the performance of ±800kV UHVDC technology. Considering the huge power export of Sinkiang and Tibet area, SGCC (State Grid Corporation of China) started R&D of higher voltage level UHVDC technology on 2008. Considering the capacity and distance of power transmission, the economics of different voltage level development were evaluated as well as the feasibility of key equipments. On the end of 2010, several key parameters are decided. For the 10,000MW power transmission over 2350kM or longer, the selected rated voltage is ±1100kV, and rated current is 4750A with capacity 10,450MW. In addition, the R&D schedule is presented. In this paper, the current R&D progress and the scheduled study of ±1100kV UHVDC are presented. The content is organized into six parts. In part I, the basics and operation status of Xiangjiaba-Shanghai project is given. Then, the demand of ±1100kV project is introduced, as well as pilot project. In part II, the R&D progress of key technology is given. Main circuit scheme and the technical specification of equipments are introduced. The main circuit configuration is same with Xiangjiaba project. The two series converter scheme is connected with equivalent voltage distribution in one pole. By optimizing the configuration and parameters of surge arresters, the over-voltage level is suppressed deeply including AC side and valve side of transformer, critical points in DC circuit, etc. The insulation level is also proposed. The study of external insulation and electromagnetic environment, are presented, which have significant impact on the project construction cost. The length of insulators and air clearance are proposed., In third part, the R&D progress of key equipment is introduced. Firstly, the crucial points of all DC equipments are reviewed, and give possible solution. Secondly, the roadmap and technical solution of converter transformer and wall bushing is discussed, In part IV, the scheme of converter transformer on-site assembling is proposed. Due to the transportation limit, it is impossible to transport the whole transformer to Sinkiang area by railway or road. Then, the on-site assembling idea is proposed and studied. In the scheme, the high-end valve hall of pole II is used for transformer assembling. The current technical solutions are introduced including manufacture, fault treatment and test. In addition, the preliminary manufacture and test equipment layout in valve hall is also given. Then, this paper discusses the key points in the solution, and ideas. In part V, the R&D of next step is presented.