Authors: Shengtao Li
Source: FERMAT, Volume 21, Communications 17, May-Jun., 2017
Abstract: In recent 30 years, the demand of electricity in China presents a huge increase. It is expected that China’s installed power capacity and electricity consumption will reach 1640 GW and 8.4x1012 kWh by 2020, respectively, doubling the figures of 2010. However, the large coal, hydro, and wind power bases are mostly located in the western and north regions, approximately 800-3000 km away from the load centers. This situation drives China to develop long distance, large capacity, efficient, economic and clean energy transmission technology to meet rapid development of China. Ultra-high Voltage (UHV) transmission shows lots of advantages, such as the huge transmission capacity, the low power loss, saving transmission corridors, saving the unit costs, and so on. So, China has been committed to the UHV AC and DC development in the past decade.
During the development of UHV AC/DC transmission systems, some key issues needed to be solved. Such issues include electromagnetic environmental and noise control issues, key equipment manufacturing, system security and stability, and some related insulation issues etc. To solve the above technical issues, the related industries of UHV were organized and four steps of developing routes were put forward by China. During 2005 to 2008, China has made a lot of UHV achievements, such as technical innovation in UHV equipment, UHV bushing design and manufacture, electrical field optimization, and UHV test facilities construction. Most of the key equipment, including transformer, shunt reactor, bushing, arrest, control and protection system, and gas insulated switchgear (GIS), are the first successfully developed in the world, and their performances are excellent. To develop UHV bushing process, the UHV AC and DC optimal design platform was established to optimally design various bushings, such as transformer bushing, oil-SF6 bushing, wall bushing, and so on. The developed XJTU-formula composite with excellent dielectric properties is widely used in manufacture of UHV bushings. Through electric field analysis and simulation of the whole substation, UHV DC valve hall and transmission line, the corona noise of UHV substations was greatly decreased and electromagnetic environment control means and methods of UHV transmission line were proposed. In addition, a lot of UHV test facilities were established, including UHV AC test base, UHV DC test base, Tibet high-altitude test base, simulation center, high power laboratory, and R&D center. These test bases provide lots of useful experience for the construction of UHV projects.
After solving the key issues in UHV development, China began to construct UHV engineering practices. In January 2009, the Jindongnan—Jingmen 1000kV UHV AC Pilot project with the transmission distance of 640km was put into operation. In July 2010, the Xiangjiaba—Shanghai 800kV UHV DC Pilot project with transmission distance of 1891km was put into operation. By the end of 2014, there were three UHV AC and four UHV DC transmissions constructed and put into operation. These projects, which were independently developed, designed and built by China, present the features of feasibility, safety, and economy.
Based on the China’s UHV plan in the future, more than 14 links will be constructed, including 13 ±800kV UHV DC and 1 ±1100kV UHV DC transmission lines by 2020. Among them, the Zhundong—Wannan ±1100kV UHV DC transmission system which will reach the world’s highest voltage class, the largest transmission capacity (12000MW) and the longest transmission distance (3300km) will be constructed. To solve the new challenges caused by the increasing voltage level, China has launched studies on key technology of ±1100kV UHV DC transmission in 2009 and some progress has been made. Upon these projects, China also made plans for medium and long term power flow pattern, including the construction of “Global Energy Internet” and the forming of cross-border and cross-region interconnections in the global context.
Index Terms: Ultra-high Voltage, Transmission, AC/DC, Insulation.
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