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The 3,293 kilometers Changji-Guquan 1,100 kilovolt (kV) ultrahigh-voltage direct current (UHVDC) link, capable of transmitting 12,000 megawatts (MW) of electricity is the world’s longest DC transmission system with the highest voltage and power capacity ever
The challenge was in keeping equipment compact
“When State Grid approached us to develop this technology, we realized how enormous the challenge is,” said Gerhard Salge CTO for Hitachi ABB Power Grids. “The 1,100-kV project was a huge step in voltage and transmission power, breaking all records of projects currently in operation and setting new paradigms for the future of sustainable power transmission.”
The voltage level was the key challenge. Just like lightning, electricity naturally wants to leap to the earth and, the higher the voltage, the further it can leap. This means all the equipment had to become more powerful and larger than ever before.
Yet the biggest technical challenge was not increasing the rating of the transformers, bushings, capacitor banks and breakers but keeping them compact and the size under control, simply to keep the transportation, execution and sites manageable. It was here, in the development and design of the 1.1 million volts electrical equipment, that the most significant breakthroughs were made.
Additionally, an innovative indoor design for the capacitor bank was developed to ensure power quality of the system.
Global expertise for solving local site-specific challenges
During the execution of this project, many other non-technical challenges had to be overcome, not least the harsh environment in Changji, which is located deep in the Gobi Desert.
“For such important infrastructure projects, the time schedule will always be very tight with many difficulties, uncertainties and risks,” said Julia Xiaojan Li, Hitachi ABB Power Grids Transformers Project Manager for the Changji site. “In a normal location this would be enough of a challenge but the environment in the Gobi Desert is really very harsh. The temperature during the winter time, even during day time, can be minus 20 centigrade.”
From 800-ton transformers, to vast arrays of semiconductor converter valves, capacitors and breakers; Hitachi ABB Power Grids supplied a huge variety of technologies combined with advanced HVDC system design engineering, bringing together its best engineers from across the world to meet the customer requirements. To reduce transportation distances, local manufacturing facilities were built but even items from these “nearby” factories required a 300-kilometer journey before reaching the final location.
Saving millions of tons of CO2 emissions
Through a colossal team effort, the system was completed, transmitting power with as much as 40% lower losses (compared to a conventional transmission system). Less energy is wasted, and more power reaches end users, saving millions of tons of CO2 emissions.
The link has now been in commercial operation for over a year, suppling power from the Xinjiang region in the Northwest, to Anhui province in eastern China. The 12,000 megawatts of electricity – the equivalent of 12 large power plants – is enough power to provide for around 12 million people.
What does this mean for the World?
“This project shows that UHVDC technology is ready to transmit power more than 3000 kilometers in a safe and reliable way. In fact, this transmission distance makes cross continental interconnections possible,” said Magnus Callavik, HVDC Global Engineering Manager, Hitachi ABB Power Grids. “Another very exciting project underway in China is the Zhangbei, 4-terminal, meshed HVDC grid project which will integrate up to 4,500 megawatts of renewable power for Beijing and the 2022 winter Olympics. Together, these two milestones in the development of HVDC shows that the road to a globally interconnected grid of the future is open.”
About Hitachi ABB Power Grids, Ltd.
Hitachi ABB Power Grids is global technology leader with a combined heritage of almost 250 years, employing around 36,000 people in 90 countries. Headquartered in Switzerland, the business serves utility, industry and infrastructure customers across the value chain, and emerging areas like sustainable mobility, smart cities, energy storage and data centers. With a proven track record, global footprint and unparalleled installed base, Hitachi ABB Power Grids balances social, environmental and economic values. It is committed to powering good for a sustainable energy future, with pioneering and digital technologies, as the partner of choice for enabling a stronger, smarter and greener grid. https://www.hitachiabb-powergrids.com