InnoPower

Nexans Supplies Fault Current Limiter to Applied Superconductor Ltd. 2009-4-22
Nexans has supplied a superconducting fault current limiter (FCL) to Applied Superconductor Limited (ASL) for a one-year pilot installation in the UK. ASL is currently installing and commissioning the component into an 11kV substation in Lancashire. Jean-Maxime Saugrain, Corporate Technical Manager of Nexans’ Energy Infrastructure Division, stated that ASL and Nexans had a history of cooperation that Nexans intended to continue, with new projects in the pipeline. Saugrain said that the installation site has a typical operating regime and high safety needs. “Low average currents with highly peaked large inrush currents allow for the operation with a comparably small cryocooler. The FCL, which is deployed in a bus-section configuration, effectively in parallel with the existing bus-section circuit-breaker (which of course will be left open during the test) must limit the fault contribution, from the healthy to the faulted busbar when a fault occurs on an outgoing circuit.” The project is being undertaken by a consortium comprising ASL and three Distribution Network Operators (DNOs). The consortium will deploy three superconducting FCLs in a pilot project involving UK distribution networks. The three participating DNOs are CE Electric UK, Electricity North West (until recently United Utilities) and ScottishPower EnergyNetworks. AC Losses Substantial Challenge The project is part of an ongoing effort by Nexans to develop FCL with high power ratings. According to Saugrain: “For higher power ratings—meaning currents in the many kA range—AC losses are still a substantial challenge. Improvements are anticipated from the progress in HTS conductors with reduced AC losses, and the development of moderate-cost cryocoolers with higher cooling power, efficiency and better user-friendliness should make wider applications possible.” Saugrain said that Nexans is committed to fully testing its medium-rated FCLs before moving forward: “At present we are more focusing on the medium voltage level to establish both production and operating experience before projecting transmission level FLCs. We consider it reasonable to make one development step after another.” Saugrain stated that scaling to higher power ratings aside, scaling up the production capability for FCL manufacturing was a process that would take time, but that would indeed occur. “With the large fabrication background of Nexans, scaling up the production to large series levels is more an aim than a challenge. Of course, market penetration will not happen overnight. We are confident that our rise in production capacity will keep pace with the rising requests.” Proven Operation Key to Technology Adoption Saugrain said it is important for utilities to get accustomed to new technologies before integrating new devices on a larger scale: “The installation should show safe and reliable operation over a reasonable period of time of all the components and accessories involved.” Joachim Bock, Managing Director of Nexans SuperConductors, commented: “The threshold of superconducting FCL commercialization is being crossed with this project. Further limiters for medium-voltage applications and with varying specifications are in production. Adapting them to specific customer needs, such as to protect power plant auxiliary networks, can easily be achieved, thanks to the modular nature of the device.” Saugrain elaborated: “Former installations had typically been funded projects involving a research background. This current limiter now is custom designed and produced entirely in the industry. It sets standards and, due to the modular design of the device, can easily be adapted to other voltage, current, or limiting characteristics.” Nexans Emphasizes Strategic Shift from Materials to Component Manufacture In addition to developing and manufacturing the superconducting material and components for the FCL, Nexans designed and assembled the complete system, including the cryostat. The current limiter was successfully subjected to high-voltage tests and to a full series of short-circuit tests witnessed by ASL. Bock commented: “With this product we have progressed up the value chain from material via component to system, to provide our customers with the optimum solution. An effective FCL device is of great strategic importance to Nexans activities in the field of superconductors, especially in light of our work in HTS cables. Nexans believes FCLs will play an increasing role in meshed networks, in the connection of renewable generation and in future smart grids.” Nexans’s decision to design the entire FCL system required the development of new capabilities, but the company insists that the cost is worth the increased user-friendliness of a system designed by a single producer. Saugrain commented: “Nexans had to expand its fields of competence into electrical power engineering as well as system integration. However, by hiring new people we have strongly increased the multidisciplinarity of our dedicated team.” Saugrain said that there were many advantages to an integrated system. “It is an advantage for the user to have one competent partner responsible for the entire limiter system. Additionally, having all processes from first concepts to final installation in house reduces the risks adherent to interfaces. Best knowledge of the material allows the optimum integration into systems.” Nexans has developed its FCL technology independently since SuperPower terminated its contract with Nexans in 2005. SuperPower at the time said it was ending the contract based on the determination that Nexans’s Melt Cast Processed (MCP) BSCCO-2212 HTS material was not suited to its matrix FCL application (see Superconductor Week, Vol 19, No 17). Nexans at the time said it would pursue the development of its own FCL. Saugrain said that Nexans continues to use MCP HTS material for their FCL: “While steadily improving the properties of this material, we also follow all other material options, not only for FCL, but particularly also for our applications in superconducting cables, and for our group working on coated conductors.” BSCCO Advances Aid Return to Resistive Model Material Nexans said that the economics of its FCL have also improved since SuperPower withdrew from its contract in 2005. According to Saugrain: “The improvements in the BSCCO MCP material and in the current limiter components have allowed us to return to the purely resistive FCL principle. Efficient protection of the superconductor and safe and reliable limiting behavior results in a fail-safe design of the limiter, having advantages both in normal operation and in limiting mode over other concepts.” Previous FCL Demonstration at Netphen Led to Improved Cryocooler Integration Nexans has previously installed a superconducting FCL into the 10kV grid for RWE Energy in Netphen, Germany (see Superconductor Week, Vol 18, No 4). The FCL for RWE was designed for 10MVA operation and was also based on MCP BSCCO-2212 elements developed with support from the German Federal Department of Education and Science (BMBF). The project in Netphen was removed after its one-year trial period, but Saugrain said it provided the grounds for several improvements in their FCL system: “After some initial difficulties with the cryocooler integration, the FCL proved safe with the reliable operation of all components involved in the grid for almost one year. All faults induced by the grid were handled safely and according to expectations. Unfortunately there was no full 3-phase short during this period. “Progress in material properties and homogeneity, as well as improved concepts for the component design, had enhanced the FCL module parameters. Other cooling philosophies, like GM cryocoolers, or automated feeding from dewars lead to more reliable cryogenic concepts.” From：Superconductor Week No. 2304