With the development of cities, there are many underground pipe networks in many big cities. It is more and more difficult to install and lay traditional cable, and the cost of installation and maintenance will be greatly increased. By using the existing pipe or cable tunnel and replacing the existing conventional cable with HTS cable, the transmission capacity of underground power grid can be multiplied and the contradiction between the increase of load and the limited underground space can be solved well.
The superconducting effect has been discovered for the first time
As early as 1911, Dutch physicist h.k.ohnes discovered that mercury's resistivity suddenly decreased from the normal residual resistivity value to nearly zero when mercury was cooled to about 4.2k with liquid nitrogen. Onnes believes the resistance of mercury has dropped to zero, the first time a superconducting effect has been found.
Since then, scientists have been discovering new superconducting materials, such as copper oxide superconductors and iron-based superconductors, and have developed various theories to explain the formation of superconductivity.In short, when the temperature of a superconductor falls below the critical temperature, the resistivity becomes zero and complete diamagnetism occurs.
The advantages of HTS cables
Since the 1990s.The United States, Europe, Japan, China and South Korea and other countries and regions have carried out high temperature superconducting cable research.
Since 2000, the research on HTS cables mainly focuses on ac transmission cables, and the main insulation of cables is also in the form of cold insulation. At present, HTS cable has basically completed the laboratory verification stage, and gradually began to enter the practical application.
Compared with traditional power cables, superconducting cables have the advantages of low loss, large transmission capacity, small cable size, strong system security and stability. Cold insulated HTS cables have low mutual electromagnetic influence and low thermal field influence, and have stable current-carrying capacity. Therefore, they have a great development prospect in the underground cable system in densely populated cities or the application of specific large-capacity power transmission.