Superconducting technologies for a controllable and reliable high capacity grid

Summary form only given. Superconductor technologies offer solutions to critical problems facing the power transmission and distribution grid today and will play a major role in the smart and high capacity grid of the future. The best known of these technologies is superconductor underground power transmission cable. By virtue of its high current density and low losses, it offers high power capacity, avoiding higher transmission voltage levels, with minimal local environmental impact, either thermal or electromagnetic, which enables installation in the midst of a dense underground network of services typical of urban environments. Particularly cost-effective will be retrofit installations through existing conduits, avoiding the digging up of city streets. Less well known is the low inductive impedance of the shielded dielectric superconducting cables, which can relieve an entire overloaded network and enable AC current control through the use of a phase angle regulator. A variety of precommercial demonstrations are underway around the globe. SuperVAR(tm) dynamic synchronous condensers, rotating machines based on high temperature superconductor rotor coils are another key technology for the future grid, the first of which is already in a beta site today. These machines provide a high level of reactive compensation on short time scales, by virtue of their remarkably low synchronous reactance which stems from their compact and iron-free design. Typically packaged in containers, these compact condensers can be conveniently sited at substations or directly at load or generation sites throughout the grid and will have a major impact in stabilizing the grid against voltage instability and outage. They complement advanced power electronic solutions which are already being sold commercially. Superconductor fault current limiters are another key technology which addresses the critical problem of ever rising fault current levels in ever growing urban environments. This equipment exploits the superconductor transition to the normal resistive state above a critical current. Prospects for commercial application of this technology are enhanced by progress in commercializing advanced higher temperature superconductor wire.