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Composite Conductor Concepts: A Piece of the Power Puzzle?
12-26-02
Issues related to electrical energy supply and demand have dominated the news, especially in the aluminum industry. While much of the attention has been on the generation of power, there are also aspects of power transmission and distribution to be considered. Two concepts under development and test, both involving the use of composite materials in the construction of the conductor, may offer some attributes that could contribute to the long-term solution.
First, a brief overview. An article in the Summer 2000 issue of Aluminum Now on aluminum and aluminum alloys in electrical conductors entitled "Track Record Points to Market Growth Potential", described the opportunities for aluminum-based conductor products in both the utility and building wire products areas. With respect to the utility products specifically, the article notes that few new transmission grids have been added since the 1960s and that we may be reaching a point where all the excess transmission capacity is being utilized. The article pointed to brownouts in the Northeast and Midwest U.S. as indicative of the overloading of the installed electrical grid. In the area of growth opportunities in utility products, it was suggested that increasing the size of conductors to reduce line losses would be one route. Also noting the deregulated utility environment, the article suggests that cost savings could be realized by utilizing life cycle costing rather than the traditional first cost method employed by the industry prior to deregulation in evaluating replacement or upgrades. These factors are the background for developments in somewhat "exotic" conductor concepts that will be discussed below.
One concept that is under development by 3M is called Aluminum Conductor Composite Reinforced (ACCR), building on the system of acronyms commonly employed in the aluminum conductor industry. The ACCR product is a lightweight, high performance conductor reinforced with 3M aluminum matrix composite wire. The composite wire is aluminum reinforced with 3M patented NextelÔ alumina ceramic fibers. Compared to steel, the composite wire has three times the strength to weight ratio, four times the electrical conductivity, less than half the thermal expansion, and reduced corrosion sensitivity. Employing these properties in an electrical conductor allows an increase in ampacity, the current carrying capability of the conductor, by 1.5-3 times. Alternatively, 7-15% lower losses at equivalent ampacity can be realized.
3M sees these composite conductor solutions as being a reconductoring solution in which no tower or foundation modifications or new right-of-ways are required. In addition, the high strength to weight ratio of the conductor lends itself to long span crossings, either in new construction or reconductoring. A data package has been developed by 3M for a 26/7 conductor with 1350 aluminum reinforced, and other constructions including a 26/7 conductor with Al-Zr alloy with a composite core for higher temperature applications and compact constructions are also under development. Further information can be obtained from 3M by contacting Dr. Herve Deve, Technical Manager, Electrical Products Div., at hedeve@mmm.com.
A second approach to improving the weight and conductivity characteristics of
utility transmission and distribution lines is to replace the steel core with
a polymer matrix composite. This product development was undertaken through a
Department of Energy-Office of Industrial Technologies Inventions and Innovations
grant to W. Brandt Goldsworthy and Associates, Inc. of Torrance, CA. The concept
involves the use of a low cost glass fiber for reinforcement of a polymer matrix,
produced as a core through a proprietary manufacturing process. The glass fibers
have 2.5 times the strength of steel, and again provide advantage in the conductor
construction through the excellent strength-to-weight ratio. Through a low cost
manufacturing process, the product is projected to be competitively priced vs.
steel-core conductors, based on the Project Fact Sheet available on the DOE-OIT
web site at www.eere.energy.gov.
Article provided courtesy of The Aluminum Association
www.aluminum.org
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