The Changji-Guquan ultra-high-voltage direct current (UHVDC) transmission line in China is the world’s first transmission line operating at 1,100kV voltage.
Owned and operated by state-owned State Grid Corporation of China, the 1,100kV DC transmission line also covers the world’s longest transmission distance and has the biggest transmission capacity globally.
The transmission line traverses for a total distance of 3,324km and is capable of transmitting up to 12GW of electricity.
Construction on the £4.7bn ($5.9bn) transmission project was started in January 2016 and completed in December 2018.
Originating in north-west China, the annual transmission capacity of the line is in the range of 60-85TWh which is enough to meet the demand of 50 million households in east China.
Benefits of the Changji-Guquan UHVDC transmission system
The Changji-Guquan UHVDC transmission line, also known as the Zhundong-Wannan transmission line or the Zhundong-South Anhui transmission line, is intended to ensure energy security in the most populated areas in east China by delivering electricity generated in the less-populated north-western region of China.
North-west China has witnessed a steady growth of new electricity generation capacity over the last few years.
The 1,100kV long-distance DC transmission project is expected to reduce the annual coal consumption by power plants in east China by 38 million tonnes (Mt) a year.
The Changji-Guquan UHVDC transmission project also promotes the development of Xinjiang Uygur region in north-west China.
In full operation, the transmission project can supply power to eight 500kV and two 1000kV AC lines.
The Changji-Guquan UHVDC power transmission line originates at the Changji converter station, in the Changji Hui autonomous prefecture of Xinjiang Uygur autonomous region in northwest China.
The overhead transmission line passes through Gansu, Shaanxi and Henan provinces as well as the Ningxia Hui autonomous region to terminate at Guquan, Xuancheng city, in the southeast Anhui province in east China.
Long-distance power transmission from Xinjiang
The Changji-Guquan line is the second major UHVDC transmission line originating from Xinjiang after the Southern Hami-Zhengzhou 800kV transmission line that was brought in to operation in 2014.
The 2,210km-long transmission line starts from the Hami Nanhu converter station in Xinjiang, and passes through Gansu, Ningxia and Shaanxi provinces to terminate at Zhengzhou in the Henan province in central China. It has a transmission capacity of 8GW.
The Xinjiang Uygur autonomous region transmitted over 71.24TWh of electricity to the Chinese national grid in 2019.
ABB supplied converter transformers, HVDC converter valves, bushings, tap changers, DC circuit breakers, as well as wall bushings and capacitors for the project under a £271m ($300m) contract awarded in June 2016.
Each of the transformers provided by ABB measures 32m-long and weighs approximately 800t.
Siemens supplied 587MVA transformers for the Guquan converter station. The transformers were manufactured at Siemens’ factories in Germany and China. Each transformer measures 37.5m-long, 14.4m-high and 12m-wide, and weighs approximately 909t.
Changji-based Tebian Electric Apparatus Stock Company (TBEA) supplied 607.5 MVA convertor transformers for the Changji converter station.
The transformers supplied by TBEA measure 33m-long, 12m-wide, and 18.5m-high.
Far East Cable Company supplied transmission wires for the Changji-Guquan UHVDC transmission line.
State Grid DC Engineering Construction Company and State Grid Anhui Electric Power Engineering Supervision Company were awarded the project management contract for the Guquan converter station.
Guangdong Electric Power Design Institute (GEDI) carried out survey works and provided design for the DC grounding electrode current field at the Changji converter station.
Qingdao XingYue Iron Tower Company supplied steel towers for the Henan section of the project.
Nanjing Electric Group, a subsidiary of Baiyun Power Group, supplied toughened glass insulators for the project.
Shandong Taikai Isolating Switch Company supplied isolation switches and grounding switches for the project.
Sun.King Power Electronics Group supplied the filter capacitor for the Changji converter station.