The Operation Statistics and Analysis of HVDC Transmission Systems in State Grid Corporation of China 2006-2012

摘要

In consideration of the unbalanced distribution of the economy progress and nature resources in China geographically, the HVDC transmission systems are playing more and more important roles in energy conservation, emission reduction, and the optimization of resources allocation. The SGCC's (State Grid Corporation of China) service area covers 88% of China's territory, and there are already 14 HVDC and UHVDC (Ultra High Voltage Direct Current) transmission systems operating in this area, which is the longest in transmission line length, and the largest in transmission capacity in the world. HVDC systems are showing their superiorities in transmitting power from the large thermo power, hydro power centres to load centres in middle China and the east coastal areas, moreover, they also play important roles in providing conventional and emergent power supply between regions, or even countries, and in sending power to remote areas. At the same time, as the concept of a strong UHV interconnection power system is being promoted, more HVDC and UHVDC systems are under planning and construction. To improve the reliability of the operating HVDC systems, and to provide a full view of the operating HVDC conditions in SGCC, it is important to make an operation statistics and analysis of the HVDC systems. This paper analyses the HVDC, UHVDC and Back-to-Back HVDC systems' (BTB) annual operation data, and makes an assessment of the systems' operating condition from the aspects of power output, forced outage, commutation failure, etc. To begin with, this paper introduces a profile of the operating HVDC systems in SGCC, and evaluates the transmission capacity from the aspects of electricity delivery and operation ratio. Also, this paper introduces an index of forced energy unavailability to show the influence of operational incidents on the transmission capacity. After that, the mono-pole, bipole and converter forced outage times of SGCC's HVDC systems from 2006 to 2012 are categorized to quantitatively evaluate the safety level of HVDC transmission channels. As to the reasons for forced outages, the reasons causing system failure like extreme weather and equipment failure are categorized and discussed through typical cases. Moreover, the commutation failure statistics of HVDC systems in one particular year are also shown in the paper, with typical cases to discuss on the operation risk of the power grid caused by grid faults and equipment defects. At last, this paper discusses on the operational status and vulnerabilities of the HVDC systems of SGCC in summary, and provides advices to improve the safety level of the power network and increase the transmission capacity of HVDC systems.