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DISTRIBUTION CONDUCTORS

One area in the electrical power industry that has undergone extensive change is the type of

conductors available to transmit and distribute electricity. Copper was the first metal used to

transmit electricity during the development of the electrical industry in the early 1880s. Copper

conducting sizing for distribution was determined by strength requirements, with load

requirements as a secondary factor. From the standpoint of efficient electrical conductivity and

ampacity, conductors were generally larger than required. Because of the weight of the copper

conductors, span lengths were short, thus increasing the overall cost of the distribution line.

Aluminum began replacing copper as the metal of choice for transmission and distribution

conductors around 1895 in California. Since that evolution, aluminum has been used by electric

utilities for the transmission and distribution of electric power. Aluminum rank second only to

copper in volume conductivity and possesses a conductivity to weight ratio twice that of the

copper. Its strength to weight ratio is 30 percent greater than copper.

With the introduction of the aluminum conductor as a transmission and distribution conductor,

the need for a conductor with a greater strength to weight ratio was soon realized. In 1907, a new

aluminum steel composite cable, which combined light weight aluminum with the high strength

of a steel inner core, was introduced. This new steel reinforced aluminum conductor became

known as ASCR and rapid acceptance through 1939.

Soon after, an all aluminum – 

 magnesium – 

 silicon alloy was introduced. The new all – 

 

aluminum alloy cable (AAAC) had comparable mechanical and electrical properties to ACSR,

 but improved weight and corrosion resistance characteristics. More recently, new alloys have

 been developed to provide thermal stability, increased conductivity, vibration resistance, and

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other specific characteristics. There are four types of overhead conductors used in the industry

for electrical transmission and distribution. These conductors are as follows:

  AAC (all –  aluminum conductor)

  AAAC (all  –  aluminum –  alloy conductor)

  ACSR (aluminum conductor, steel reinforced)

  ACAR (aluminum conductor, aluminum  –  alloy reinforced)

Transmission and distribution systems usually contain a combination of these conductors in

various configurations, all uniquely designed into total system whose primary purpose is to

deliver electrical power to the consumers.

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AAC CABLE

AAAC CABLE

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ACSR CABLE

ACAR CABLE