| Extra-high voltage,large capacity and cross-regional power transmission is an important way to realize "power transmission from west to east" and an effective means to promote the optimal allocation of energy and resources.At present,the extra-high alternating and direct current transmission system,as the way of "power transmission from west to east",has played a crucial role in ensuring energy security,improving energy efficiency and promoting sustained economic growth.With the orderly construction and promotion of AC and DC transmission projects of different voltage levels,China's major power networks have gradually stepped into a new stage with UHV power grids as the main grid and all levels of power grids developing in a progressive manner.At present,the national air pollution prevention and control plan is being implemented step by step.It has become the primary task of the UHVDC transmission and maintenance unit to master the operation characteristics of UHVDCt transmission system and timely analyze the problems and experience encountered in field operation and maintenance.The Puqiao UHVDC transmission system from Puer of Yunnan to Jiangmen of Guangdong province is the second west-east transmission channel of China southern power grid after the Yunguang project.On the basis of reliable operation of the Yunguang direct current transmission system for many years,its successful operation has accumulated valuable experience for field technicians.However,compared with traditional HVDC systems,UHV DC systems are characterized by rich operation mode,various regulation methods,complex control protection process.After years of operation,some logical defects or risks of control protection system in UHVDC transmission system are gradually exposed.This paper simply expounds the different operation modes of the UHVDC transmission system,composition,basic principle and logical function of AC/DC station control,pole control systems,group control system,the valve group protection system.The protection action of 82 BPS I section of two stations and the undefined process and reason of the Qiaoxiang station pole 2 high end valve group in the unlocking process of DC pole 2 low end valve group of the Puqiao DC power transmission system and the reasons of undefined high end valve group are analyzed.This paper analyzes the influence of the failure of the position detection signal of bypass circuit breaker in different converter stations on DC controlprotection,and also explores the risk that the failure of the position detection signal of the bypass circuit breaker of single valve group in the rectifier station may lead to the blocking of single pole double valve group.Aiming at the defects or risks exposed in the actual operation of the system,this paper analyzes and studies the control and protection action strategy of the Puqiao UHVDC transmission system,after detailed analysis and demonstration of the problems in the operation of the UHVDC control protection system,relevant control measures and the protection optimization scheme of 82 BPS I section are proposed to improve the reliability of the UHVDC transmission system.In order to improve the reliability of the Puqiao DC transmission system,the problems in the operation of the UHVDC control protection system were analyzed and demonstrated in detail,and relevant control measures and the protection optimization scheme of 82 BPS I were proposed.It will provide useful reference for the operation and maintenance of UHVDC control protection system in the future.Some optimization methods have verified the correctness of the optimization measures through engineering practice,which can improve the stability of UHVDC system operation to a extent. |
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