You are here

Fully Encapsulating Dielectrics for Gaseous Helium Cooled Superconducting Power Cables


TECHNOLOGY AREA(S): Ground/Sea Vehicles

ACQUISITION PROGRAM: PMS320, Electric Ships Office; PMS501 Littoral Combat Ship Program Office

OBJECTIVE: Develop an encapsulating medium voltage dielectric material and application process to electrically insulate a high temperature superconducting power cable and end terminations in a gaseous Helium environment.

DESCRIPTION: The Navy is embarking on an aggressive and innovative Power and Energy Program and a Next Generation Integrated Power System (NGIPS) for application on both shore based operations, future surface ships, and underwater vehicles. With the advent of prime mover power generation and high power directed weapons, the Navy is striving to distribute an order of magnitude increase in electrical power without increasing distribution system space and weight or reducing efficiency. The Navy requires cost-effective, innovative technology solutions that fulfill these requirements to ensure that next-generation vessels are able to accomplish their mission.

Future naval power systems are trending toward a fully integrated power system, which leverages installed electrical generation to meet the high power demand of future loads. The electric propulsion loads are within the range of 20-80 MW. The ability to distribute this amount of power in an integrated power system requires increased distribution power densities over what is currently available through conventional copper cabling. High temperature superconductors (HTS) are an ideal candidate for the technology to increase volumetric and gravimetric power distribution densities that will meet the demands of future shipboard power loads.

HTS power cables have matured and proven reliable through land-based programs including multiple in-grid installations (ref. 1 and 4). In addition to providing an excellent cooling medium, the liquid Nitrogen used in these demonstrations provides key dielectric insulation to the cable. Due to safety and logistical requirements for naval applications, liquid Nitrogen is not a viable option for shipboard HTS applications. As an alternative to liquid Nitrogen, the Navy currently uses cryogenically cooled Helium gas to cool HTS degaussing systems (ref. 2). Although Helium is known to have poor dielectric strength, it is not a concern as HTS degaussing is a low voltage system.

For voltage applications approximately 20kV, the weak dielectric strength of Helium warrants dielectric solution that eliminates a Helium path between phases in the HTS cables. This would require the development of a novel dielectric material or process of application to hermetically encapsulate the HTS conductor phases. This novel material or process would support the ability to develop a HTS power cable operating in gaseous Helium at the extreme temperature range of 30-50K. Any solution identified in this topic is required to be applicable to a coaxial DC HTS power cable as well as 3-phase triaxial AC cable. The dielectric material and application process may be extended to a multi-phased HTS power cable termination (ref. 3 and 5). Dielectric strength of a proposed solution should exceed 100 kV/mm, with a breakdown voltage greater than 100kV. The proposed solutions should be able to be applied to each phase of a HTS cable in a manner that does not induce damage to the conductor. This requires the HTS conductor not to exceed a temperature of 160C. The cost of the proposed solution should not exceed $25 per meter per phase of HTS cable.

PHASE I: The company will define and develop a concept for a material and process of applying an encapsulating dielectric material suitable for a 20kVDC HTS power cable and terminations in Helium gas at appropriate density ranges (0.7 kg/m3 to 19.8 kg/m3). The technical feasibility of the proposed concept will be identified and demonstrated through modeling, analysis, and bench top experimentation where appropriate. The solution shall be quantified in terms of dielectric size, weight, and cost. The Phase I final report shall capture the technical feasibility and economic viability for the proposed concept that can be matured further if awarded a Phase II. The Phase I Option, if awarded, should include the initial layout and capabilities description for the material or process to be developed in Phase II.

PHASE II: The company will develop and fabricate a prototype HTS power cable based on the Phase I work and Phase II statement of work (SOW) for demonstration and characterization of key parameters of the dielectric insulation system. Based on lessons learned in Phase II through the prototype demonstration, a substantially complete design of a cable and termination should be completed and delivered to enable Navy qualification testing. The prototype will be evaluated against the predicted benefits identified in Phase I for size, cost, and dielectric strength. The prototype will be delivered at the end of Phase II. A Phase III plan shall be developed to transition the technology to the Navy.

PHASE III DUAL USE APPLICATIONS: The company is expected to support the Navy in transitioning the HTS power cable and termination insulation technology for Navy use. This may include teaming with appropriate industry partners to incorporate the developed dielectric material into a fully qualified power cable for interested acquisition programs including PM501 and PMS320. The company will develop technical data specifications and manuals as needed to support transition of a fully qualified system. The desired electrical power converter has direct applications in commercial power grid, power distribution, electric power conversion, and cryogenic power applications making it broadly applicable to the commercial world.


    • J.F. Maguire, J. Yuan, W. Romanosky, F. Schmidt, R. Soika, S. Bratt, “Progress and status of a 2G HTS power cable to be installed in the long island power authority (LIPA) grid,” IEEE Transactions On Applied Superconductivity, Vol. 21, 2011, 961.


    • J.T. Kephart, B.K. Fitzpatrick, P. Ferrara, M. Pyryt, J. Pienkos, E.M. Golda, “High temperature superconducting degaussing from feasibility study to fleet adoption,” Transactions on Applied Superconductivity, Vol.21, 2010, 2229.


    • H. Rodrigo, L. Graber, D.S. Kwag, D.G. Crook, B. Trociewitz, “Comparative study of high voltage bushing designs suitable for apparatus containing cryogenic Helium gas,” Cryogenics 57, 2013, 12;


    • Demko, J.A; Sauers, I; James, D.R.; Gouge, M.J.; Lindsay, D.; Roden, M.; Tolbert, J.; Willen, D.; Trholt, C.; Nielsen, C. T., "Triaxial HTS Cable for the AEP Bixby Project," Applied Superconductivity, IEEE Transactions on, vol.17, no.2, pp.2047,2050,


  • Shah, D.; Ordonez, J.C.; Graber, L.; Kim, C.H.; Crook, D.G.; Suttell, N.; Pamidi, S., "Simulation and Optimization of Cryogenic Heat Sink for Helium Gas Cooled Superconducting Power Devices," Applied Superconductivity, IEEE Transactions on , vol.23, no.3, June 2013;

KEYWORDS: Dielectric; HTS; superconductivity; integrated power system; high-energy demands for Naval ships; HTS power cable;

  • TPOC-1: Jacob Kephart
  • Phone: 215-897-8474
  • Email:
  • TPOC-2: Jason Miller
  • Phone: 215-897-8925
  • Email:

Questions may also be submitted through DoD SBIR/STTR SITIS website.

US Flag An Official Website of the United States Government