ACCR Frequently Asked Questions

3M™ Aluminum Conductor Composite Reinforced Frequently Asked Questions

  • 3M™ Aluminum Conductor Composite Reinforced (ACCR) is a proven, high temperature, low sag (HTLS) overhead transmission conductor. Designed as a replacement for similar sized ACSR and ACSS, it provides up to twice the ampacity with less thermal expansion (sag) while maintaining or improving mechanical loads, tensions and clearances on existing structures.
  • Depending on the application, 3M ACCR can carry two or more times the current of a standard conductor of comparable diameter. It has less weight and sag, but the same strength and can be installed to meet your tension and clearance requirements. This allows you to maximize the capacity of your transmission upgrade using existing structures and rights of way. Compared to a rebuild project, you can get your upgrade done faster and with fewer permitting requirements.
  • 3M ACCR has been installed at voltages ranging from 6 kV to 500 kV and can be used any place standard conductor can. It is typically used when large capacity increases are required, usually 50% or higher, especially where thermal limits are an issue. Its thermal properties and strength-to-weight ratio can solve difficult siting challenges, including ampacity upgrades with clearance constraints, long spans or difficult terrain (rivers, canyons); extreme climatic conditions (corrosion or ice and wind loading); and environmentally or politically sensitive areas (wetlands, dense population). It is also used on new lines over spans where shorter or fewer towers are important for siting and permitting.

    See Customer Installations for examples.

  • 3M ACCR allows you to quickly increase capacity across constrained areas, enabling access to least-cost or renewable generation, while using existing towers and rights of way. It also provides capacity increases on N-1 contingency paths to support a flexible and reliable system by maximizing path ratings. And, 3M ACCR is a tool when thermal constraints cause compliance issues with NERC reliability standards.
  • Because 3M ACCR's core is aluminum-based, rather than steel, it is somewhat more conductive than steel core conductors of the same kcmil resulting in lower losses under the same operating conditions. In addition, 3M ACCR comes in a trapezoidal wire design that can improve conductivity up to 28% compared to the same size, round wire ACSR.

    Transmission upgrades often require many changes that can affect line losses. Losses are calculated as the square of the amps times the resistance of the conductor. Therefore, the actual line losses will vary based on a number of factors, including the size of the conductor, the amount of energy flowing down the line at various times, ambient conditions such as temperature and wind speed, and the duration of various levels of current flow. Our technical support experts can work with you to determine a more accurate estimate of the impact on your line.
  • The impact of a transmission upgrade on carbon depends on a number of factors, including the calculation method. One important factor is the reason for the upgrade. If it is being done to enable renewable generation, doing it faster with 3M ACCR can yield benefits. Estimates indicate that getting just one MW of renewable generation on the grid one year earlier than it otherwise would have been could save approximately 2,300 MMT of annual emissions.

    Also, while both construction and reconductoring require conductor and accessories, reducing steel and concrete tower and foundation production and transportation may also reduce carbon impacts. The exact effect on CO2 will vary depending on the project.

    According to the Union of Concerned Scientists, existing state renewable portfolio standards will require 76,750 MW to be installed by 2025, resulting in 183,000,000 MMT of annual carbon dioxide emission reductions.
  • By eliminating the need for expensive new towers, foundations and construction; land acquisition; lengthy and controversial permitting processes and long construction outages, upgrading with 3M ACCR can offer substantial savings even at a higher conductor cost-per-mile. 3M ACCR can also provide more capacity for the same size conductor as even other high temperature low sag conductors, maximizing the value and longevity of your upgrade.

    See Customer Installations for examples.
  • Since the product was officially launched over a decade ago, the U.S. price for 3M ACCR has decreased approximately 60%, including a pricing change in 2015. International pricing is also much reduced, after accounting for currency fluctuations. Potential customers who evaluated the product back then are now finding that 3M ACCR is economically attractive for a broader range of projects. If you have questions regarding pricing for your specific project, please contact your sales professional or email us.
  • The differences between 3M ACCR and other conductors are due to differences in materials. 3M ACCR's core wire is composed of all aluminum-based components. In addition, it uses a high temperature, hardened aluminum zirconium for the outer wires. This material combination offers two main advantages over other high temp, low sag conductors – ampacity and durability.

    High temp, low sag conductors that rely on steel or other metals such as nickel alloy are heavier than the same diameter 3M ACCR. Therefore, even when sag performance is improved, the same capacity cannot usually be gained without compromise – rebuilding or raising towers, installing taller towers, increasing the tension, or, in some cases, putting up a smaller conductor under higher tension, which increases losses. Therefore, 3M ACCR offers the maximum capacity increase without adding the risk of modifying the structures, often reducing siting and permitting requirements.

    Conductors relying on carbon polymers as the core material may not have comparable durability. Thermoset matrices are more prone to degradation if exposed to heat, ultra-violet rays (sun) or moisture, as found both by 3M and other researchers. Testing performed in the U.S. and China indicates that the core starts to degrade and show permanent deformations at temperatures as low as 150° C. At 170° C strength is reduced, and some of the reduction may be irreversible.1

    Testing in the U.S. also showed mechanical failure at tensions as low as 93% of rated breaking strength, as well as under excessive bending. As a result, the maximum recommended tension loading may be as low as 80% of the catalog RBS.2 Known failures of these conductors either during installation or operation have occurred in the U.S., China, Poland, South Africa and Indonesia.

    Carbon composite conductors using thermoplastic as the core matrix rely on a material with a glass transition temperature between 85 and 100° C, close to the temperature rating of ACSR. The glass transition temperature (Tg) is the temperature at which polymers transition from a hard state into a molten or rubber-like state. The impacts of a low Tg on high temperature operations of the conductor are not fully understood.3

    Some high temp, low sag conductors achieve their sag performance by using a softened, or annealed, aluminum for the conductor outer wires. However, softened aluminum is harder to handle during installation and is more prone to damage than a hardened aluminum, such as used in 3M ACCR. Replacing hardened aluminum with softened aluminum also yields a loss of strength. Galvanic corrosion can be a problem if aluminum is used with materials that contain steel or carbon. Coatings or barriers are required to prevent corrosion. However, because 3M ACCR is all-aluminum-based, it is corrosion resistant without barriers that can be damaged during handling or installation.

    Therefore, 3M ACCR is the only conductor on the market with its unique blend of sag and capacity performance and durability, resulting in more than a decade of reliable, successful installations. And it is the only conductor supported and backed by 3M, a company doing business for over 100 years, more than 60 in the utility industry.

    3M believes that 3M ACCR is substantially similar to the competitive products on the basis of form, fit and function. Please see 3M product specifications for detailed product information. All data presented here is based on publicly available information compiled from respective manufacturers as of September 2014 and is believed to be reliable, but the accuracy or completeness is not guaranteed.
    As always, before using the 3M product, you must evaluate it and determine if it is suitable for your intended application.

       1See Electric Power Research Institute, "Aging Assessment of a Composite Core High-Temperature Low Sag (HTLS) Conductor," February 11, 2009. See Also Leveque, David, Anne Schieffer, Anne Mavel and Jean-Francois Maire, "Analysis of How Thermal Aging Affects the Long-term Mechanical Behavior and Strength of Polymer-matrix Composites," Composites Science and Technology, Volume 65, Isssues 3-4, March 2005, pp 395-401. See also, Kumar, Bhavesh G., Raman P. Sing and Toshio Nakamura, "Degradation of Carbon Fiber-reinforced Epoxy Composites by Ultraviolet Radiation and Condensation", Journal of Composite Materials, pp. 2713-2733, Vol. 36, No. 24, 2002. See also, Burks, B.M., D.L. Armentrout, M. Baldwin, J. Buckley, M. Kumosa, "Hybrid Composite Rods Subjected to Excessive Bending Loads," Composites Science and Technology, 69, 2009, p. 2625-2632. See also Li, Rui, Hon-yun Yu, Chang-shui Yu and Jun Cao, "Some Questions Should be Paid Attention on ACCC Application", Electrical Equipment, Volume 9, No. 5, May 2008.

       2See Freimark, Bruce, et. al., "Sequential Mechanical Testing of Conductor Designs," 2009 Electrical and Substation Structures Conference, IEEE, November 8-12, 2009.

       3Fortron® Design Manual FN-10, Ticona, 1999
  • 3M ACCR is installed on 5 continents and in a variety of applications, including areas with significant ice loading or corrosive conditions; densely populated, fast growing urban areas; environmentally sensitive installations; and critical lines.

    See Customer Installations for examples.
  • 3M ACCR looks no different than conventional ACSR and will not change the appearance of an existing line if installed on the same structures. Except for being slightly larger, the accessories look and install like conventional accessories, but are designed for use at higher temperatures and with the core material.
  • 3M offers both standard round wire and compact (trapwire) conductors in several common strandings and in sizes ranging from 130 kcmil to over 2000 kcmil. Other size and construction options are available based on the specific requirements of your application.
    Visit our Technical Information page to see Product Data and Properties of 3M ACCR in some common sizes. You can also download the PLS CADD cable files.
  • 3M ACCR is specifically designed to be installed much the same as ACSR. Equipment differences are minimal. Larger diameter sheaves and bullwheels are required. Roller arrays should be used for break over towers and certain angles. Also a tensioning grip, rather than a Chicago or pocketbook grip, should be used. Check the Installation Guide for details in our Technical Information page. You can also watch videos of an actual installation.

    Because the outer wires are hardened aluminum, they are more resistant to damage and bird caging during installation than ACSS and ACCC, which use annealed aluminum. In addition, we offer installation training and support during your project.
  • Yes. 3M, in cooperation with industry-recognized accessory suppliers, developed a complete set of accessories. Although these accessories are designed especially for use with the 3M core material and higher operating temperatures, they are similar to conventional accessories, as is the installation process. AFL Conductor Products (AFL) provides compression-type hardware, and Preformed Line Products (PLP) provides helical-rod type. See Accessories in our Technical Information page.
  • When you select 3M ACCR, you can enjoy the peace of mind of using a technology backed by the technical resources of 3M.

    Conductor selection – Our experienced engineers work with you to match the best 3M ACCR options to your needs, given your capacity, mechanical, clearance, environmental and budget constraints.

    Supply chain – We can work with you to refine planning and logistics and incorporate any additional project requirements into your project plan. We develop a project profile and bill of materials and manage accessory and equipment orders.

    Installation – Although the equipment and installation process for 3M ACCR are similar to those for ACSR, our installation experts will ensure your crews understand them so the conductor is successfully installed. And if any questions arise during installation, we'll be available to answer them.

    Click on Contact Us to get help with your project.

    Visit our Technical Information page to review the 3M ACCR Installation Guide.
  • 3M ACCR has undergone unprecedented thorough and rigorous laboratory and field testing. The results have verified product specifications and performance, even in extreme environments and operating conditions; demonstrated the conductor's strength and durability, even when operated at high temperatures for long periods of time; and validated the line design coefficients, even after extended use.

    Multiple conductor constructions were tested to yield basic design parameters such as tensile strength, stress-strain curves, creep exponents, thermal expansion coefficients, sag-temperature-tension response, weight, diameter and electrical resistance. All tests showed that the materials behaved as expected and that the behavior on a transmission line can be predicted using standard transmission design software and approaches. Data is provided in laboratory and field tests and is embedded in conductor design offerings.

    Once basic design data were obtained, the constituents, conductor, and accessories were subjected to a wide range of standard and accelerated tests designed to provide life-aging data and confidence in the longevity of the conductor and accessory system. Where possible, existing test standard protocols were used or, if necessary, were adapted to reflect the greater performance range of the system (e.g., higher temperatures). Data was collected to address the following, using the approaches noted:

    • Conductor motion: Aeolian vibration, galloping
    • High mechanical loads with extreme cold
    • High temperature accelerated aging
    • Thermal cycling
    • Fault current behavior
    • Lightning strike resistance
    • Corrosion behavior
    • Environmental resistance: humidity, UV, temperature
    • Impact resistance: ice-shedding, gunshots

    After the life-aging study, the materials were then moved out into the field for testing under both conventional and accelerated operating conditions. Controlled testing was done at an outdoor installation at Oak Ridge National Lab. The conductor was also installed in a number of actual utility grid applications. You can see a complete set of Field & Lab Tests in our Technical Information page.

    Since that time the conductor has undergone a variety of testing and qualification by customers in the U.S., China, Mexico and Europe.
    In all cases, the conductor has passed, verifying both product specifications and performance.
  • Visit our Technical Information page where you can download typical conductor properties in English or metric versions, or you can download the PLS CADD™ files. The conductor data is also featured in SAG10®. If you'd like us to answer specific questions, Contact Us to request additional information or get contact information for an account manager.