The United States, the former Soviet Union, Japan, and Italy have all built AC EHV test lines and carried out extensive research and testing of AC EHV transmission technology, with only the former Soviet Union and Japan eventually constructing AC EHV lines.
1150kV project in the former Soviet Union
The 1000kV AC system in the former Soviet Union has a rated voltage (nominal voltage) of 1150kV and a maximum voltage of 1200kV, which is the highest among the existing projects in the world. A total of 2350km of 1150kV transmission lines and four 1150kV substations (one of which is a booster station) were built in the former Soviet Union in August 1985. Of these, 907km of lines and three 150kV substations (one of which was a booster station) operated at the system-rated voltage of 1150kV for five years from 1985 to 1990. Later, due to the economic and political break-up of the former Soviet Union, the whole line was downgraded to 500kV by the KAZAKHSTAN Central Bureau of Dispatch and the design of the overvoltage protection system did not need to be modified during the entire period of operation and operated well.
1000kV projects in Japan
The 1000 kV power system in Japan is concentrated in the Tokyo Electric Power Company, which began construction of the 1000 kV transmission and substation project in 1988 and completed two 1 000 kV transmission lines with a total length of 430 km and a 1000 kV substation in 1999. The first is a 1000 kV transmission line from the atomic power plant on the Sea of Japan coast in the north to the Tokyo area in the south, called the North-South Line (length The second is a 1,000 kV transmission line connecting power plants along the Pacific coast, called the East-West line (240 km in length), the East Gunma main line and the South Chime City main line. All 1000kV lines and substations have been operating at a reduced voltage of 500kV since their construction and were to be upgraded to a rated voltage of 1000kV in anticipation of the construction of nuclear power plants along the Pacific coast and the Tohoku region, but the construction of power supplies and the planned upgrade to 1000kV has been significantly delayed due to the stagnation of load growth, and the upgrade to 1000kV is not expected until the late 2110s.
Italian 1050kV pilot project
In the 1970s, Italy and France were commissioned by the International Federation of Western European Power Generation and Supply (IFES) to carry out a demonstration of the choice of 800kV and 1050kV transmission options for the European continent, after which the Italian UHV AC transmission project undertook a series of basic technical studies and equipment manufacture under the auspices of the State. The 1050kV test project was completed in October 1995. In December 1997, the project was carried out at the nominal voltage of the system (nominal voltage) of 1050kV for more than 2 years and specific operational experience was gained.
The test project is located at the 1000kV test station in Suvereto, Italy, and consists of two parts:
(1) a 1050/400kV substation;
(2) a 2.8km 1050kV transmission line. a single-line schematic of the 1050kV test project is shown in the diagram.
China Extra High Voltage Transmission Project
1000kV Extra High Voltage AC Pilot Demonstration Project
China’s research on ultra-high voltage transmission technology began in the 1980s, and after more than 20 years of efforts, a number of important scientific research results have been achieved. The research shows that the development of UHV transmission is an inevitable choice for the development of China’s power industry. The State Grid has already and is in the process of developing the following UHV AC transmission projects: firstly, the middle line project of Shaanxi – Southeast Jinan – Nanyang – Jingmen – Wuhan, and secondly, the eastern line project of Huainan – South Wan – North Zhejiang – Shanghai. In addition, China’s third UHV transmission project – “Sichuan-Shanghai ±800 kV UHV DC Transmission Demonstration Project”, also started construction in Yibin County, Sichuan Province on December 21, 2007. By 2020, China’s ultra-high voltage power grid will be basically completed, and the power transmission will reach more than 200 million kilowatt hours, accounting for 25% of the total installed capacity of the country.
On January 6, 2009, China’s independent research and development, design and construction of independent intellectual property rights of the 1000 kV AC power transmission project – Jin southeast – Nanyang – Jingmen ultra-high voltage AC test demonstration project successfully passed the trial operation. This marks a major breakthrough in the localisation of China’s long-distance, high-capacity, low-loss ultra-high voltage (UHV) core technology and equipment, which is of great significance in optimising the allocation of energy resources and ensuring national energy security and reliable power supply.
This world’s first operational UHV AC line is 640 km long, with the highest voltage level in the world, reaching 1000 kV, transmitting five times more power than the existing 500 kV, saving more than half of the power loss and floor space in the transmission process, and saving one-third of the investment of the whole project compared to the 500 kV line. It spans across the three provinces of Jin, Henan and Hubei, which also contains two large crossing sections of the Yellow River and Han River. The line starts from the Shanxi 1000kV Southeast Jinjiang Substation, passes through the Henan 1000kV Nanyang Switching Station and ends at the Hubei 1000kV Jingmen Substation.
The project was approved by the National Development and Reform Commission in August 2006 and construction commenced at the end of the same year. The project was fully completed in December 2008, with the commissioning of the system completed and put into trial operation on 30 December and the 168-hour trial run completed and put into commercial operation at 22:00 on 6 January 2009.
On 15 December 2015, the world’s first 10-megawatt extra-high voltage DC transmission project – Ximeng-Taizhou ±800kV extra-high voltage DC transmission project – commenced construction in Xinghua. The project is an important part of the “four crosses and four straight” UHV project under the National Action Plan for Air Pollution Prevention and Control, and is scheduled to be completed and put into operation in 2017.