Superconductor Power Cables

High-capacity, very low impedance superconductor cables are now being deployed in live grid cable projects – paving the way for a brighter, more secure electricity future.

Increase reliability and security of the power grid. Because they can be designed to be smart and controllable, HTS cables can make the power networks in which they are installed self-protecting. Self-protecting secure power networks adjust rapidly and automatically to disruptions in power network equipment caused by weather, willful destruction or other factors.

Significantly lower impedance than conventional cables. HTS cables can be placed strategically in the transmission grid to draw flow from overtaxed conventional cables or overhead lines — and relieve network congestion. Very low impedance cables can help solve grid congestion problems and enable implementation of new grid configurations.

Today's congested power grid and environmental pressures are requiring utilities to look for new solutions to solve power flow problems that address the growing concern over siting and quality of life issues in urban and suburban communities. High-capacity, low-impedance HTS cables offer significant benefits over conventional overhead transmission lines and copper cables. By replacing copper wie with HTS wire in power cables, these systems are able to carry as much as 10 times more power, making them an ideal soluton for netowrk upgrades and urban retrofit projects. They support load growth, enable cost-effective controllability of power over a meshed grid, and can be implemented with low environmental impact. Major features of HTS power cables are:

• Up to 10 times more power capacity supports new
  generation and load growth
• High power capacity at lower voltage enables easier siting and reduced ancillary systems costs
• Ideal solution for breaking urban power bottlenecks
• Improved cost-effective control of power flow across meshed grids
• Extends the operating life of existing high-load corridors
• No electromagnetic field emissions, no soil heating, and no oil results in low environmental impact

At the heart of the superconductor power cable is HTS wire that conducts more than 150 times the electrical current of copper wire of the same dimensions.  Using conventional cable stranding machines, multiple strands of HTS wire are woven into a coaxial configuration.  Once woven ito a coxial configuration, an HTS cable produces essentially zero Electromagnetic Field (EMF) emissions. The inherently low impedance of this cable assembly enables cost-effective control of power flows over the surrounding grid network. Liquid nitrogen, the dielectric and coolant of choice to maintain the HTS wire at its operating temperature, is inexpensive, abundant and environmentally safe, eliminating the oil used in many conventional power cables in cities across the U.S.

Comparison of power equivalents of overhead power lines, copper underground cables, and HTS underground cables.

The very high power capacity and very small footprint of the cables makes them much easier to site, especially in dense, older urban areas. The compact size and low environmental impact of HTS cables offers new ways for grid planners and operators to upgrade and increase the capacity of electric distribution networks.

Their low impedance construction enables cost-effective control of power flow, enabling power to be pumped economically and reliably into congested areas and transferred precisely where it is needed to relieve the congestion.  American Superconductor is working in partnership with the world’s leading power cable and commercial refrigeration companies to apply revolutionary HTS wire to new underground cable solutions to eliminate costly grid bottlenecks.

There are several principal designs for superconductor power cables.  The figure below illustrates a cold dielectric design  To see illustrations of the four principal superconductor power cable architectures, click here.

Example HTS cable design by Nexans

More information on the benefits of HTS power cables – fitting more power into existing space