Superconducting cables, subverting cable tradition

High-temperature superconductors are one of the greatest discoveries of the
20th century.
The zero resistance of superconductors is even more subversive for traditional wires and cables with copper and aluminum as conductors
.
As more high-temperature superconductors are discovered, it is not ruled out that superconducting technology will be applied
on a large scale in the cable industry.
Superconductivity refers to the property
that when the temperature of conductive materials is close to absolute zero, the resistance of the material under the thermal movement of the object molecules tends to 0.
"Superconductor" refers to a conductive material
that can carry out superconducting transport.
Zero resistance and diamagnetism are two important properties
of superconductors.

One of the greatest uses of the zero-resistance property of superconducting materials is for power
transmission.
Ultra-high voltage transmission carries large losses, and the use of superconductors minimizes losses, so that power is delivered to users
almost without loss.
According to statistics, about 15% of the electrical energy lost by copper or aluminum conductors is on the transmission line, and in China alone, the annual power loss is more than 100 billion kWh
.
If it is changed to superconducting transmission, the energy saved is equivalent to the construction of dozens of large-scale power plants, and the results of the major project "35 kV high-temperature superconducting cable system engineering application and demonstration research" led by the Shanghai Electric Cable Research Institute have passed the appraisal of the China Electricity Council, and some key parameters have reached the international leading level
.
At the same time, the second-generation high-temperature superconducting material industrial-grade production line was built in Shangchuang Superconducting Technology Co.
, Ltd.
, which solved the problem
of material localization of superconducting cables.

In 1911, Dutch scientist Onnes accidentally discovered that when mercury is cooled to minus 268.
95 °C, its electrical resistance suddenly disappears, a phenomenon known as superconductivity
.
However, minus 268.
95°C is close to absolute zero (minus 273.
15°C), and expensive liquid helium is required to bring the temperature down to that low
.
In 1986, Bernoz and Müller of IBM Labs first discovered high-temperature superconducting materials, which greatly increased the critical temperature so that it could reach "zero resistance"
in a low-cost liquid nitrogen cooling environment.

30 years have passed, and through the efforts of scientists around the world, the second generation of high-temperature superconducting materials has reached the "critical point"
of market-oriented applications.
At the IEEE conference co-organized by Shanghai University and other countries, superconducting experts from more than 10 countries, including China, the United States, Germany, France and Japan
, discussed together.
Bennard, director of the Institute of Engineering Physics at the University of Karlsruhe, Germany, said that the institute cooperated with Nexans to build Germany's first kilometer-level high-temperature superconducting cable commercial line in Essen, which has been in stable operation for more than
a year.
After evaluation, German authorities believe that superconducting power transmission technology has matured
.
In Bennard's view, "Shanghai's high-temperature superconducting technology is very internationally competitive, and it is just the right time
to achieve industrialization.
" Moreover, China's economic development is faster than Germany's, and there are more infrastructure projects, providing a broad space
for superconducting cable applications.
”

Compared with traditional copper and aluminum material cables, what are the advantages of high temperature superconducting strip cables? Cai Chuanbing, chairman of the conference and director of Shanghai Key Laboratory of High Temperature Superconductivity, said that the current-carrying capacity of superconducting cables can reach more than 100 times that of copper and aluminum wires, and the cable cross-sectional area is small, which is more suitable for high-current, high-energy electricity occasions; With the "zero resistance" performance, the superconducting cable has no loss during transmission, and the energy saving effect is remarkable
.
According to statistics, the transmission loss rate of China's power grid is 8% to 10%, and the annual loss is equivalent to the annual power generation
of three nuclear power plants.
Superconducting cables also have their weaknesses, such as insufficient technology maturity and high engineering construction costs
.
In this regard, Xin Ying, a professor at the School of Electrical and Automation Engineering of Tianjin University, said that at present, the industrialization of high-temperature superconducting cables in China has reached a threshold, and how to cross it, 50% depends on technical improvement, and the other 50% depends on the concept of
relevant departments.

The one-time investment of superconducting cable system engineering is large, and the cost can be recovered by virtue of superior performance after long-term operation, but the current financial system is not conducive to the establishment of such projects
.
The cadre tenure system will also affect the launch of the superconducting power grid, because the cycle of obtaining economic benefits is longer, and the cadres have a short tenure in a post, which objectively leads to conservative decision-making
.
The application of Shanghai research superconducting cables to power grid engineering as soon as possible does depend on the concept of the power sector and large power users
.
In addition, the whole life cycle evaluation of the Shanghai research superconducting cable should be carried out as soon as possible to prepare
for its application in the power grid demonstration project.

Superconducting cables are most suitable for high-density electricity areas in large cities, and Shanghai has the conditions to take the lead in building the first high-temperature superconducting cable line
connected to the power grid in the country.
In the process of building a science and technology innovation center with global influence, the participating experts suggested that the city provide greater engineering application space for superconducting cables, superconducting machines and other products, and occupy the commanding heights
in the tide of industrialization of high-temperature superconducting technology.

With the development of superconducting technology, the world's cable giants have also begun the research and development
of superconducting cables.
South Korea's LS Cable, Japan's Furukawa Electric Co.
, Sumitomo Electric, France's Nexans and many other world's large cable companies have made achievements in superconducting cables, and the commercial operation of superconducting cables is also gradually advancing
.
On November 19, 2014, South Korea's LS Cable launched the 80KV500MW DC superconducting cable transmission system experimental project
.
The superconducting cable produced this time is 20% thicker than ordinary copper cables, but the power transmission is 10 times that of ordinary copper cables; In May 2015, the world's first train equipped with superconducting cables was successfully put into trial operation in Japan, and its superconducting cables can transmit
power under a superconducting state of minus 196 degrees.