STI - Superconductor Technologies Inc.

STI has been a world leader in commercializing HTS technology since 1987

High Power HTS Transmission Cable

Superconducting High Power Transmission Cable transmits 5 to 10 times the electrical current of traditional copper or aluminum cables with significantly improved efficiency.

HTS power cable systems consist of the cable, which is comprised of 100s of strands of HTS wire wrapped around a copper core, and the cryogenic cooling system to maintain proper operating conditions.

HTS superconducting cables offer solutions for utilities facing challenges that include:

	Substation footprint availability,
	Lack of available rights of way, and
	High load connections between substations.

HTS power cables are particularly suited to high load areas such as the dense urban business districts of large cities, where purchases of easements and construction costs for traditional low capacity cables may be cost prohibitive.

At this time, the cost and performance of 2G HTS Wire are major limiting factors for broad commercialization. STI's plan is to reduce cost and increase performance of HTS wire.

HTS Cable Market Applications:

	HTS power cables act as a bridge between electric energy transmission and distribution. Transmission voltages range from 60 kV to 765 kV and distribution voltages range from 5 kV to 46 kV.
	The primary application is for a medium voltage feed to load pockets in dense urban areas. In these high demand zones the grid is often saturated with aging infrastructure. HTS technology brings a considerable amount of power to new locations where the construction of additional transmission to distribution substations, with major transformer assets, is simply not feasible.
	Another potential use of HTS power cable is to improve grid power transmission by connecting two existing substations. In dense urban environments many substations often reach capacity limits and require redundant transformer capacity to improve reliability. HTS cables can tie these existing stations together, avoiding very costly transformer upgrades and construction costs.

Steps Towards Commercialization:

	While market interest in 2G HTS wire for AC Power Cable applications is extremely high, the industry is struggling to lock in a consistent supply.
	Market commercialization is also highly dependent upon cost reductions for cable components like the HTS wire, cryostat and cooling stations.
	Industry wide, HTS wire needs significant performance improvements to enable wide commercialization. Cable manufacturers are currently using wire carrying close to 100 Amps/cm width. This low current capacity requires cable producers to buy more wire to achieve the desired current density. Higher capacity wire will increase current density and decrease the amount of wire required. Cable manufacturers believe that approximately 500 Amps/cm width is the ideal wire performance.

What is HTS Power Cable?

	There are several unique configurations utilized to construct an HTS power cable.
	One superconducting cable design is the Triax. This proprietary configuration winds three phases concentrically on a single inner copper core. This superconducting cable design integrates each AC phase into a single cable stacked on top each other.
	A second cable design consists of three separate, single-phase, cables encapsulated in a single cryogenic envelope.
	A third type of HTS cable uses three individual, single-phase cables, with each encapsulated in an individual cryogenic envelope.
	Constructing superconducting high power transmission cable requires a great deal more HTS wire than one might expect. Independent of the design, each cable type contains hundreds of strands of layered HTS wire. Strands of HTS wire are wound around a core in a one direction and then the next layer is wound in the opposite direction. This process is repeated many times. Cable manufacturers use more than 400 kilometers of HTS wire (4mm wide @ 90 A/cm) to construct a single kilometer of superconducting power cable.
	The number of HTS wire strands is determined by the wire performance. The higher the performance (increased current density) the fewer strands are required for the same power capacity. Thus, a significant increase in wire performance will greatly reduce the number of wire strands/layers needed to produce the same length power cable today, thus cutting product cost and manufacturing time for the cable manufacturer.

What is the difference between 1G and 2G HTS Wire?

	Companies that currently produce 1G HTS wire are migrating to 2G HTS wire because of its superior performance in the presence of a magnetic field, improved mechanical properties, and lower cost.
	2G HTS wire is designed to be able to replace 1G HTS wire in form, fit, and function, and expected to surpass 1G wire in electrical performance and overall economics. 2G wire is fabricated utilizing a completely different production process. 2G wire deposits HTS material layers onto a thin, flat, metal substrate.
	2G wire essentially looks like tape – a thin, narrow strip of metal. It requires no powder or rods to be bundled with other rods, as does 1G Wire, and has the potential to be highly cost effective to produce.
	When creating the 2G wire standard, the HTS industry made the significant decision to use YBCO as the preferred HTS compound. STI has been developing and producing HTS products using YBCO for over 15 years. In fact, STI devloped a proprietary manufacturing method to attain the best cost and performance in the industry.
	Today, HTS wire producers are challenged to scale their 2G wire manufacturing capacity to meet industry volume, cost and performance requirements. STI's 2G wire product roadmap is on track to aggressively address each of these challenges.