These systems require new control technologies, but do not require any change to the distribution system materials. Beta Engineering has designed and built numerous high voltage projects across the country. Take a look at selected projects from our portfolio to find out more about the EPC solutions Beta can provide for you. About Services Projects Careers Contact.
Why Beta? All Services. Business Development Team. Sales Representatives. The transport of electrical current and levitation are two of the most important areas of practical importance for the application of superconductors.
These are based respectively on the two most important fundamental properties of the superconducting state: flux expulsion through the Meissner effect and the vanishing of resistance.
Superconductivity for energy applications is mainly concerned with the latter property, as it depends on the ability to carry lossless electrical currents for the purpose of power transmission and for the construction of extremely powerful electromagnets for use in generators and motors, and for other applications such as high- energy particle accelerators and nuclear fusion where intense magnetic fields are required.
Superconducting conductors allow a scaling down of size which is of importance for plasma confinement in fusion. A type-II superconductor enters the mixed state in the presence of a magnetic field B that is higher than the lower critical field B c 1. The motion of the vortices leads to an electric field within the superconductor and hence resistance and power dissipation, rendering the conductor unattractive for lossless current carrying applications.
A major effort has been spent in engineering pinning strategies to prevent or greatly reduce the motion of flux vortices. Flux motion also tends to progressively broaden the resistive transition with increasing B. We discuss here some intrinsic fundamental phenomena that can alleviate the ill effects of vortex motion. The most straightforward vortex free state arises when the applied B is less than the lower critical field. The origin of B c 1 is related to the difference in free energy that results from the insertion of a vortex in the superconductor: the lost condensation energy because of the normal vortex core versus the reduction in the magnetic field energy because less flux is excluded and the B field lines are less crowded.
Usually B c 1 has a rather low value in extreme type-II superconductors because of the very short coherence length and core size, and consequently smaller volume of missing condensation energy compared to the reduction in magnetic field energy because of typically large demagnetization effects. However this situation can change when a sample with a high aspect ratio such as a film is placed in parallel field.
Under these conditions B c 1 becomes greatly enhanced with respect to its usual bulk value and was shown by Abrikosov to be [1] :. Another vortex excluding condition occurs when the cross section of the sample parallel to the applied B becomes too small. The swirling vortex supercurrents become strangled by the walls. As a result of this self feeding process, at some point the vortex core explodes and Abrikosov vortices can no longer exist.
This process was studied theoretically by Likharev and he found the critical cross-sectional dimension to be [2] :. A third novel low-dissipative condition arises in a two-band superconductor when vortex electric fields become delocalized and one of the bands becomes normal but with a high normal conductivity at high B. A principal cause of the viscous drag is the Ohmic dissipation in and around the vortex core resulting from local electric fields generated by the acceleration of superfluid resulting from the motion of the vortices.
This is the reason flux-flow resistance grows with B and the resistive transition broadens with B [3] - [5]. In this case, the electric field will extend throughout the sample and you have scenario of the delocalized vortex electric field [8]. Additionally if the superconductor has two bands, one of which is driven normal and has high normal-state conductivity, then the majority of the dissipation takes place outside the vortex core and throughout the entire volume of the superconductor.
This now leads to a viscous coefficient that grows with B and hence the flux-flow resistance does not increase with B and resistive transitions will not broaden. This scenario is realized in disordered MgB 2. Transport measurements were conducted in a Cryomech pulsed-tube closed-cycle refrigerator with the magnetic field supplied by a GMW water-cooled electromagnet.
The cold tip was positioned within the magnet pole pieces and the magnet was mounted on a rotating platform. Unlike conventional lines, superconducting transmission lines have conductor AC losses. There is no generally accepted physical model to describe these losses, so much of the data is empirical.
There are also losses due to imperfect thermal insulation of the superconducting cable. The result is a thermal leak between the cold liquid nitrogen and the warm surroundings. The losses can be reduced but not eliminated by creating a vacuum between the superconducting cable and the thermal insulator. Finally, there are small losses due to joints and terminations of cables. The load placed on the line is of particular importance. The same is certainly not true of conventional transmission lines.
A big reason for this is that power is dissipated as the square of the current run through the line. As the load is increased, the losses in the line increase quadratically. At this point, superconducting lines could only possibly be a sensible alternative to conventional lines if they are placed in a high load setting. Large cities offer the perfect setting for superconducting lines, as they often demand large amounts of electrical power.
American Superconductor and Consolidated Edison have agreed to build and test prototype superconducting transmission cables in the New York City infrastructure [4]. Publisher: American Association for the Advancement of Science. Document Type: Article. Length: 6, words. Translate Article. Set Interface Language. Decrease font size. Increase font size. Display options. Default More Most.
0コメント