特高压交、直流输电的适用场合及其技术比较

Applicable occasions of UHVAC/UHVDC transmission and their technology comparisons in China

从世界范围看,特高压输电技术将长期发展。根据中国电网的发展趋势,特高压电网将由1000kV级交流输电系统和±800kV级直流系统组成。根据特高压交流和直流2种输电方式不同的技术经济特性,比较分析了两者的适用场合,并对特高压输电线路的防雷保护、可靠性、稳定性、电磁环境、绝缘子选型和交直流配合等技术问题,分别展开比较。得出主要结论:特高压交流主要定位于近距离大容量输电和更高一级电压等级的网架建设,特高压直流主要定位于送受关系明确的远距离大容量输电以及部分大区、省网之间的互联;特高压直流的正极性导线比负极性导线更易遭受雷害;应避免出现由一个大电厂通过数回特高压交流线路集中送至同一地区的情况,也要重视包含多回特高压和超高压直流线路的“多馈入直流输电系统”的安全稳定问题;建议中国特高压输电线路优先采用大吨位、高强度的合成绝缘子,并采用由数片玻璃防污绝缘子和合成绝缘子构成的组合绝缘子方式,避免合成绝缘子芯棒碳化脆断的事故发生。

From point view of the world,UHV transmission technology will develop continuously. In China,the planning UHV grid is composed of 1 000 kV AC transmission systems and ±800 kV DC transmission systems. Based on the differences of technical and economic characteristics of UHVAC/ UHVDC,their applicable occasions in China are first compared. Then,some technical problems of UHVAC/UHVDC,such as lightning protection of transmission lines,reliability,stability,and electromagnetic environment of power grid,insulator selection,and DC/AC coordination,are compared respectively. Main conclusions are therefore made as follows ：UHVAC is mainly applicable to short -distance ＆ large- capacity electricity transmission and the network construction of a higher voltage grade. UHVDC is mainly applicable to long- distance ＆ large- capacity electricity transmission with clear transmission end and receiving end,and is also applicable to the interconnections of some regional and provincial power grids. The positive transmission lines of UHVDC are more likely to be damaged by lightning than the negative ones. The case that the electricity transmission to a certain region through several UHVAC transmission lines from the same large scale power plant,should be avoided. More attentions should be paid to the safety and stability status of ＂multi- infeed HVDC transmission systems＂ with UHVDC ＆ EHVDC transmission lines. It is suggested that composite insulators of large tonnage and high intensity are prior to be used in the UHV transmission lines in China. Pollution proof glass insulators and composite insulators should be combined in use,which will avoid the brittle fracture of composite insulators.