China's First Self-Developed Superconducting Cable Operational in Shenzhen

Shenzhen - On September 28, a new superconducting cable, self-researched and produced within China, has been placed into operation here in Shenzhen.

The cable is also the first of its type in the world applied in the central area of Shenzhen, a 13 million citizen megacity, which demonstrates that China has fully mastered the core technologies of design, manufacture and construction of new superconducting cables.

The cable has a diameter of 17.5 centimeters, a length of 400 meters and a transmission capacity of up to 43 megavolt amperes which is five times that of conventional cables. Such a level of transmission capacity can meet the power demands of four, high-speed railways running concurrently by 350 kilometers per hour.

The cable is anticipated to fully ensure highly reliable power supplies to the Ping An International Finance Center in Shenzhen, the tallest building in the sprawling Greater Bay Area which encompasses Guangdong–Hong Kong–Macau.

As a major science and technology project of China Southern Power Grid, this project not only boasts 100 percent China-made key equipment but also provides a unique new global solution to the power supply challenges that confronts large populations centers, like Shenzhen, within areas of megacities that absolutely require high load electricity density.

High-temperature superconducting transmission technology has been projected as being the next-generation power transmission technology of strategic significance as it has advantages of lower electricity loss, larger transmission capacity, environmental friendliness, taking up less space in the corridor.

This exciting new technology gives full play to the conductive properties of superconducting materials … and thus the power loss in low-voltage transmission can be reduced to near zero.

The power transmission capacity of superconducting cables is much larger than that of a conventional one. To be more specific, the transmission capacity of a 10-kV three-phase concentric HTS cable is larger than that of a conventional 110-kV cable, but the transmission loss is only one quarter to one fifth of that of a conventional cable, which suits power supply in areas of high load density very well.

Shenzhen is among the growing number of major metropolis cities in China that need high load density in electricity and its CBDs have higher requirements for reliable power supplies and transmission than other areas. This project provides an “all-in-one” turnkey solution to multiple practical problems of high-power supply reliability, high load density, high power quality and limited land resources.

“If we only adopt a conventional way of power transmission or use traditional technology to increase transmission capacity, it will be very challenging to meet the electricity demands of power supplies for those business districts in Shenzhen, such as the Futian Central Business District where prices of real estate properties are high and the need for electricity is massive,” said Lyu Zhining, general manager of the innovation and digitalization department of Shenzhen Power Supply Co., Ltd., a subsidiary of CSG.

However, Mr. Lyu remarked that a 10-kV superconducting cable not only meets the current power supply demands but also reduces the use of high-voltage cables in urban power grids, simplifies the grid network and cuts down on the construction of 110-kV substations thus saving up space of 500 square meters.

With this cable is placed into operation this time required for the three-phase concentric configuration features the most compact structure with the least number of tapes used and the greatest R&D challenges. After four years of independent innovation, engineers from the project's research team made substantial breakthroughs in numerous key technologies, such as the overall design and manufacture of a superconducting cable system and the R&D of domestic GM refrigeration with large cooling capacity, making key equipment 100 percent locally produced which not only meets but exceeds the domestic technical gap.

A superconducting cable can be promoted sustainably only when its cost is market reasonable. As has been reported, the cost of superconducting tapes accounts to nearly 50 percent of the total cost of the three-phase concentric HTS cable; and compared with other configurations, this cable saves tapes likewise by 50 percent.

Additionally, the cable in operation this time uses superconductors that can still work in a liquid nitrogen cooling environment to transmit electricity, instead of the conventional Copper-Clad Aluminum conductors. When liquid nitrogen is used as a cooling medium that is relatively easy to be produced at a lower cost, the high-temperature superconductors are capable of exhibiting superconductivity at 70℃ above absolute zero and thus have promising application prospect.

To solve the bottlenecks of producing cryogenic refrigeration equipment for superconducting cables, the engineers from the project team has successfully developed the first “homemade” GM refrigerator with a large cooling capacity in China, and realized online "plug-and-play" capabilities of the refrigeration which ensures high-reliability operation of superconducting cables in the liquid nitrogen environment of minus 200℃ for a substantial time period.