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March/April 2010

Electrical Conductors

ASTM Committee B01 Celebrates More Than 100 Years of Standards Development

The standards of ASTM International Committee B01 on Electrical Conductors have been crucial to North America’s electrical grid since the early 20th century.

In his Carrollton, Ga., office at Southwire Co., Mark Lancaster, P.E., manager of overhead transmission engineering, examines a transmission line specimen that consists of six strands of copper around a hemp core. A utility company has sent the sample to Southwire’s technical group to determine whether or not the line should continue in service. The wire, perhaps originally part of a loop around a city or a line carrying power from a small generating facility, dates to 1909, says Lancaster, chairman of ASTM Committee B01 on Electrical Conductors, the year of B01’s founding.

The copper and hemp line goes back to a time when electrification in the U.S. was in its infancy; much of today’s grid was constructed in the first half of the 20th century. Preceding the system had been centuries of work by inventors and innovators to understand electricity before it could be harnessed as the convenience we take for granted today. Indeed, the National Academy of Engineering named electrification the number one greatest engineering achievement of the 20th century.

After 1877, when a Connecticut brass mill man named Thomas Doolittle developed hard-drawn copper wire strong enough to be installed overhead, electrical lines became commercially feasible. Thomas Edison perfected a practical incandescent light bulb in 1879, and the first commercial electrical station, in Manhattan, N.Y., began to provide power in 1882. And, in 1909 — 11 years after ASTM’s formation — the society’s founders considered the need for a standard for hard-drawn copper wire for electrical purposes.

A resolution by the ASTM Executive Committee called for “Committee W” to develop its first consensus document, Standard Specifications for Hard-Drawn Copper Wire. A small group of nine technical experts met twice in New York City, in April and May 1909, to come to agreement on standard requirements for hard-drawn round wire, grooved trolley wire, and cable or strand. The group agreed on the standard values for diameter and area, tensile strength and elongation, and the overall standard specification was adopted on Aug. 16, 1909.

This first specification from what would become ASTM Committee B01 has been regularly revised and reviewed over its century of existence. Today that specification is designated B1-01 (2007); its name remains the same.

Following that first hard-drawn copper wire standard came specifications for medium-hard-drawn copper wire (B2) and soft or annealed copper wire (B3) in 1912; these two documents also still appear with B01’s other standards in Vol. 02.03 of the Annual Book of ASTM Standards.

In the 1940s, Committee B01 began work on standards for aluminum wire. The light metal had become commonly used in 20th century electrical applications after World War II, notes Peter Pollak, P.E., Pollak and Associates LLC, Fairfax Station, Va., because of the dynamic increase in aluminum availability resulting from production capacity that was greatly expanded to meet demand for the light metal during World War II. Aluminum initially was available as an industrial material in commercial quantities after the 1889 patenting of a new method to extract the light metal from bauxite ore. Prior to that time, aluminum was only available in very small quantities and was considered a precious metal more valuable than gold.

B01’s longest running documents for aluminum wire cover extra hard (1350-H19) aluminum round wire (B230/B230M), extra hard lay-stranded aluminum conductors (B231/B231M) and coated-steel reinforced aluminum conductors (B232/B232M). This trio of standards, which detail conductor size, construction, mass and strength requirements, were originally published in 1948.

As local electric systems grew to serve expanding post World War II population centers, “the grid that evolved into what exists today was built using product standards from B01 specifications,” says Pollak. The result today enables several hundred thousand miles of transmission cable that feed an even greater quantity of distribution lines.

Standards for the Metals in Electrical Conductors

Strength and conductivity: these two characteristics continue to be critical to designing electrical conductors for the transmission and distribution of electrical energy. In the 100-year-old transmission line sample sent to Southwire, Lancaster notes, the hemp was used to expand and round out the copper strands, which provided the conductivity. While steel today would be a likely core for strength, and aluminum for conductivity, copper is still dominant for use in homes and offices.

Committee B01 standards cover the specifications for metals in wires and conductors throughout the electric grid. The standards also apply to a full range of wiring for electrical applications — anything that uses copper, aluminum or steel. The committee currently maintains 80 standards specifying copper, aluminum, steel and composite electrical conductors as well as terminology and test methods.

Current work by B01 addresses composite core conductors, which, together with new high temperature/high strength steels, can carry more current. “These new core materials provide industry with new options to allow them to push more power through the grid more efficiently,” says Lancaster.

Specifications are also under way in Subcommittee B01.07 on Conductors of Light Metals for fiber reinforced aluminum matrix composite core wire (WK26302) and composite reinforced lay-stranded aluminum conductors (WK26301).

In Subcommittee B01.02 on Methods of Test and Sampling Procedure, a standard for testing silver plated conductor for electronic space application (WK5820) is now under way. Additionally, tracer wire, which is frequently made from copper clad steel for additional strength and laid next to plastic pipe gas lines to make locating it easier, is the topic of a proposed specification in Subcommittee B01.06 on Composite Conductors. The subcommittee is also working on grounding materials.

Braid and ribbon flat conductors made of copper and coated with silver, nickel or tin, currently are the topic of three work items in Subcommittee B01.04 on Conductors of Copper and Copper Alloys, which is also developing a specification for tin-coated annealed copper wire. Electronic applications such as computers call for braid and ribbon flat conductors, and the materials have not been covered by established standards.

B01 Standards and the Smart Grid

A vision for an updated, modern grid designed to meet the challenges of the United States in the 21st century, according to the U.S. Department of Energy, will enhance the reliability, efficiency and security of the nation’s electricity system while reducing the energy’s environmental impact. Much of the new smart grid technology and devices still remain to be determined, however, one thing is certain: transmission and distribution lines will still be needed to carry the electric current. In North America these power lines will be specified using standards developed by ASTM International Committee B01.

Pollak says that standards such as B957, Specification for Extra-High-Strength and Ultra-High-Strength Zinc-Coated (Galvanized) Steel Core Wire for Overhead Electrical Conductors, and B958, Specification for Extra-High-Strength and Ultra-High-Strength Class A Zinc–5% Aluminum-Mischmetal Alloy-Coated Steel Core Wire for Use in Overhead Electrical Conductors, may be called for in new high performance transmission lines that will increase capabilities. Many of B01’s other specifications potentially will also be used.

“The smart grid is all about controlling power usage effectively,” says Dustin Fox, global technical manager at Fushi Copperweld Inc., Fayetteville, Tenn., vice chairman of B01 and chairman of B01.06. “Every conductor used in transmission and distribution is going to be covered in B01.”

An Enduring Contribution

Committee B01 meets twice a year, and the group of almost 80 members, who represent material and wire producers as well as utility companies, continue to work on standards that are used across North America.

“We are all working together, and really it’s for the best interest of the products and the industry,” says Lancaster. “Competitors come together and put aside their own agendas and work purely for the benefit of industry and the customer.”

Pollak adds, “Without the existing product standards from B01, the grid — the greatest engineering achievement of the 20th century — would have to be reinvented.”

For More Information

Committee B01 invites all interested people to participate in its standards development activities. For more information, click here or contact B01 staff manager Jennifer Rodgers (phone: 610-832-9694).