Per Industry Standards:
ASTM B-415 Hard-Drawn Aluminum-Clad Steel Wire
ASTM B-416 Concentric-Lay-Stranded Aluminum-Clad Steel Conductors
The reliable, uninterrupted transmission of electrical power is vital to the electric utility industry. Transmission lines carrying large blocks of power must be permanently protected against damage from lightning or the occasional fault. AFL Alumoweld® overhead ground wires, also referred to as shield wires, provide the best means of obtaining this protection. They combine conductivity, corrosion resistance, and high strength--all of the properties necessary for such assurance.
The thick aluminum cladding on each wire offers optimum protection against atmospheric corrosion while providing the conductivity important for proper operation of protective relays. The high conductivity of Alumoweld strand also reduces the temperature rise of the static wire under fault current conditions.
Due to a thick aluminum cladding, Alumoweld overhead ground wire provides one-third the conductivity of an aluminum conductor of equal size, and several times the conductivity of steel. Each Alumoweld product is tested for resistivity, a practice not generally used for common galvanized or misch metal steel shield wires, thereby ensuring the stated electrical properties of the finished product.
These electrical properties are maintained throughout the life of the line, as contrasted to the properties of inferior galvanized or misch metal steel which can deteriorate over time. Such deterioration further reduces the already low conductivity of common steel overhead ground wires.
Numerous laboratory and field tests confirm the excellent corrosion resistance of Alumoweld wire. Its strength and conductivity are permanent in any atmosphere where aluminum is satisfactory, especially those known to be corrosive from industrial or atmospheric conditions.
This assurance against corrosion is obtained through the application of a thick covering of pure aluminum which provides a substantial barrier of protective metal. This minimum cladding thickness of Alumoweld is ten percent of the radius of the wire. The cladding has a continuous, strong metallic bond to the steel core and will not crack or flake.
On the other hand, thin protective coatings like those found in aluminized steel can be damaged to the point of steel exposure even by ordinary construction methods, resulting in progressive deterioration of the coating and eventual rusting of the steel.
Laboratory and Field Tests
Laboratory tests on Alumoweld have included salt spray, 100 percent relative humidity, and flue gas tests. In all of these, the wire and strand have performed extremely well. Similar and confirming results have been obtained by field tests conducted since the introduction of Alumoweld over 40 years ago. These field tests encompass all types of exposure including marine, industrial, and rural; and have been evaluated by our own staff and by independent researchers. Sites for field tests include those considered most severe from a corrosion standpoint. Further proof of this corrosion resistance has been provided by the millions of pounds of Alumoweld which have been installed on important lines throughout the world.
Directly related to strength and sag performance is the lighter weight of Alumoweld strand. Due to its thick cladding of aluminum, Alumoweld is 15 percent lighter than a steel strand of equivalent size. This lighter weight, combined with high strength, permits Alumoweld strand to be strung to the same sags as steel with correspondingly lower tensions and lower stresses on the towers or supporting structures.
Alumoweld overhead ground wires may be sagged to provide the proper mechanical safety and lightning protection for any power conductor.