BREAKTHROUGH IN DEVELOPMENT OF SUPERCONDUCTING CABL ES

The subject of this paper is a breakthrough in the development of long-length high-temperature superconducting (HTS) cables with integrated faultc rrent limitation (FCL) property, made in the Dutch 6 km F CL Triax HTS cable project. The increase of electricity consumption and the ris ing penetration of dispersed generation together with t he extension of large-scale renewable energy sources l ead to numerous technical bottlenecks in electrical grids such as overloading, high level of fault currents, unstable voltage levels and high electromagnetic fields. New solutio ns and technologies to respond to these challenges are nee ded. Superconducting cables technology, in its mature st at , can play a significant role in solving grid bottlenecks and making energy supply reliable, consistent and susta inable. INTRODUCTION The HTS cable technology demonstrates a great poten tial in solving of grid congestion issues. An important characteristic of HTS cables is their high transport capacity. HTS cables can transport up to 10 times more power than conventional cables of comparable r adial dimension. This feature is supported by the fact th at nowadays a long-length commercial HTS tape conducto r of the latest generation (see Figure 1) can carry 300 A/mm2 when cooled to 77 Kelvin. Figure 1 A sample of HTS tape with FCL properties In addition to their large power transport capacity and low losses, modern-generation HTS cables also have an integrated fault-current limiting (FCL) property. T he HTS cables with an improved non linear voltage-current characteristic behave intelligently, adapting their impedance to the actual need of the network, see Figure 2. Figure 2 A schematic of the non-linear voltage vs. current characteristics of HTS cables In this way, this new generation of HTS cables also contributes to a stable voltage profile in a grid, while reducing short circuit currents. Moreover HTS cable s have a very small footprint, which makes them suitable for dense and urban areas with expanded underground infrastru ctures. Despite its large potential benefits, the HTS cable s technology is not yet widespread. In-field demonstrations have been made with lengths of 100-600 m, meaning this technology is still in its immature state. The currently inefficient cooling t echnology limits the length of the cables up to 1-2 km. The n ew functionality of integrated FCL capability adds req uirements on the cooling due to additional heat production. Ther efore an advanced heat management of HTS cable is needed. 6 KM HTS TRIAX ® FCL CABLE PROJECT The Dutch DSO Alliander, in partnership with Ultera TM (a Southwire/nkt cables Joint Venture) and the Delf t University of Technology (TUD), has developed an intensive R&D program with intention to develop and install in Alliander’s grid a 6 km FCL Triax HTS  cable to demonstrate high performances of the HTS cables technology in a real network. C I R E D 21st International Conference on Electricity Distribution Frankfurt, 6-9 June 2011