UHV power transmission is a major innovation in the world’s energy field in the new century. It solves the difficulties of power transmission in super-large capacity over ultra-long distances, improves power development mode from on-site balance to optimal allocation in a larger scope, and lays a foundation for the massive development and use of clean energy.
UHV power grids are composed of 1000 kV AC as well as ±800 kV and ±1100 kV DC power systems, with such significant advantages as long transmission distance, large capacity, high efficiency, low line loss, economic land occupation and high levels of security.
With great potential for grid interconnection and transmission, UHV AC is a key technology for the building of ultra large grids. The capacity, transmission distance and corridor efficiency of 1000 kV UHV AC are 4-5 times, 2-3 times and 3 times higher than those of 500 kV AC respectively, and the line loss and unit investment are 33% and 70% of those of 500 kV AC respectively.
As the so-called “intercontinental ballistic missile” in the world of power transmission, UHV DC can realize ultra-long distances and ultra-large scale power transmission. The capacity, transmission distance and corridor efficiency of ±1100 kV UHV DC are 4-5 times, 5-6 times and 1.8 times higher than those of ±500 kV DC, and the line loss and per unit investment are 25% and 40% of those of ±500 kV DC. Transmission distance can reach more than 6,000 kilometers, equal to the distance from Boston to Alaska; and its capacity can reach 15 GW which is equivalent to 3/4 of the maximum electricity load in New York State.
UHV AC Technical Indicators
UHV DC Technical Indicators
UHV power transmission is a world-class technical problem. Since 2004, the State Grid Corporation of China (SGCC) has made every effort to promote innovation and engineer-ing applications of UHV technology, and achieved comprehensive breakthroughs in technology, equipment, standards and practical projects.
We have successfully developed nearly 100 record-breaking first sets of UHV of equipment, such as single transformers, DC converter valves and converter transformers with the world’s highest voltage levels and the largest capacity and switchgears with the greatest breaking capacity.
SGCC has established UHV AC, DC, tower and high-altitude test bases, four in total, and State GridSimulation Center. It has also built a UHV test and research system with the highest test capability and technical level in the world which helps us overcome overvoltage, electromagnetic environment, large grid control and other difficult problems.
It has established a relatively complete UHV technical standard system and published 14 international standards, 50 national standards and 73 industry standards. UHV AC voltage has become the international standard voltage. The secretariats of five IEC Committees are set in SGCC.
China finished the construction of the first commercial UHV AC project in the world in January 2009, and completed UHV DC project in the world in July 2010. By the end of 2017, 21 UHV projects (8 AC and 13 DC projects) had been completed in China with four UHV projects (3 AC and 1 DC projects) under construction. The UHV projects in operation and those currently under construction represent a reach of 37,000 kilometers, with transforming (converting) capacity surpassing 370 GVA/GW and cross-regional transmission capacity exceeding 150 GW. These UHV transmission lines have become the energy highway through which electricity is transmitted from China’s West to East and from North to South. Key technology, complete equipment and engineering application of UHV AC transmission as well as UHV ± 800 kV DC transmission project have both won the special prize of National Science and Technology Awards, which are the two highest awards ever won by power and electric engineering industry in China. As the first and second person to win both of these awards, I have devoted a lot from project proposal, decision-making to project implementation, and taken the lead in tackling key technological and engineering problems. I have also put forward UHV AC overvoltage suppression measures, UHV DC 6-inch thyristor and other technical plans, led the efforts in overcoming many difficulties, and promoted the realization of a comprehensive breakthrough in UHV technology and engineering applications.
Firstly, it guarantees the power supply. At the end of 2017, China’s installed electric power capacity was 1780 GW, with per capita power consumption standing at 4600 kWh annually. As a result, the problem of electricity consumption of 1.4 billion people has been solved.
Secondly, it helps to improve energy structure. The percentage of the installed capacity of non-fossil fuels reached 38%, whilst the installed capacities of hydro, wind and solar power in China stand at 340 GW, 160 GW and 130 GW respectively, ranking No.1 in the world. Annually, clean energy can replace 750 million tons of coal for power generation, with CO2 and SO2 emissions reduced by 1.4 billion tons and 7 million tons respectively.
Thirdly, it promotes economic development. UHV grids have accumulatively transmitted 1100 TWh of power which effectively relieve the long-standing pressure of power, coal and transportation demand and the issues of surplus hydro, wind and solar power. UHV grids also stimulate clean energy development in the outbound end, lower the power supply cost (the electricity price is nearly 1 cent less than that of local coal-fired power plants) at the inbound end and turn abundant resource advantages into economic strengths in West China to release coordinated regional economic development.
Fourthly, it helps upgrade power grids. China has built up the world’s largest AC and DC hybrid UHV grid in terms of the level of voltage and scale. China has introduced its UHV technologies to Brazil. Phase I of ±800 KV Belo Monte UHV DC outbound transmission project in Brazil constructed by the SGCC went into operation at the end of 2017, and Phase II will come into operation in 2019. UHV technology is a symbol of China’s innovation which will promote grid upgrade across the world.