SGCC Sets a New World Record in UHV DC Power Transmission
Recently, the Xilingol League-Taizhou ¡À800 kV UHV DC Project was put into operation after completing a 168-hour trial operation. As an important component of China¡¯s air pollution prevention and control action plan, the project is the world¡¯s first ¡À800 kV UHVDC project, with a rated capacity of 10 GW and hierarchically connected to a receiving 500 kV/1000 kV AC grid. The success of the project marks a milestone in international UHV DC power transmission and a new world record. Previously, the highest rated capacity of an HVDC power transmission project was 8 GW and the maximum voltage of the connected AC system was 750 kV.

SGCC attached great importance to this world-class, innovative project. Leaders from SGCC presided over the identification of key technical principles and the R&D of key technologies. Over the past five years, the company brought together resources from home and abroad and organized different parties responsible for scientific R&D, design, manufacturing, testing, construction, coordination, and operation and experts from related sectors to jointly perform project-related work. Following the principle of greater reliability for greater capacity and higher voltage, SGCC overcame major challenges in ultra-large capacity DC power transmission, hierarchicalconnection system design, and equipment manufacturing. The company proposed a set of technical plans and project design plans and successfully produced a set of new DC equipment, including ultra-large capacity converter transformers that can be transported by rail, converter transformers that can be connected into 1000 kV UHV AC grid systems on grid side, 6250A thyristors and converter valves, hierarchical grid connection control and protection systems, 1100 kV AC filter circuit breakers with long electrical life, and 8-split 1250 mm2 large-section conductors. These achievements represent state-of-the-art UHV DC power transmission technology and equipment. 

Approved by the central government in October 2015, the project was completed in September 2017, after 2,701 lab experiments and 631 on-site system adjustment tests to ensure compliance with strict requirements. As a result of these efforts, all equipment was able to operate for 4 hours at rated power and for 2 hours at 1.05 times rated power, in addition to passing the 6693A direct current test. During these tests, the equipment demonstrated excellent performance, completely fulfilling expectations. 

The innovative success of the project further consolidated and enhanced China¡¯s leading position in HV power transmission, improved the country¡¯s global influence, and drove the manufacturing quality of electrical engineering equipment to new heights. The development and application of the hierarchicalconnection technology made it possible to directly connect UHV DC power transmission projects to UHV AC grids. With HVDC and AC systems supporting each other, UHV AC/DC grids will be more flexible and safer. In this regard, the project is of great significance.

Environmental protection is of great importance in project construction. SGCC has adopted stricter ecological governance measures to comprehensively follow the national requirements on environmental protection and soil and water preservation and fulfilled its social commitment to promote environmentally-friendly and green projects.

The current project spans five provinces, autonomous regions, and municipalities, including Inner Mongolia, Hebei, Tianjin, Shandong, and Jiangsu, with two converter stations built in Xilingol League and Taizhou. It has a converting capacity of 20 GW and a total length of 1628 km. The project is able to deliver 55 TWh of clean electricity from Inner Mongolia to load centers in Eastern China, which can eliminate the need to transport 25.2 million tons of coal and reduce soot emissions by 20,000 tons, SO2 emissions by 124,000 tons, NOx emissions by 131,000 tons, and CO2 emissions by 49.5 million tons. This will promote clean development, coordinated regional development, energy structure transformations, and air pollution prevention and control, while ensuring reliable power supply. In this regard, the project is of significant economic and social benefits.

Source: Department of DC Construction of SGCC

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