Wires and Cables

The greatest portion of electrical power is transmitted through wire and cable. Wire and cable are employed either bare or insulated. The type of insulation used is dependent upon the surrounding conditions of where the conductors are to be installed.

A wire is generally considered a single strand conductor and is classified in sizes by American Wire Gage numbers  to 4/0. A cable on the other hand is generally considered a multiple strand conductor in which a strand is either a single wire or a group of wires. The sizes of cable are classified under the American Gage numbers up to 4/0. Above 4/0 the sizes are designated by their circular mil areas.

Stranded cables are further classified in the manner in which their strandings are arranged. The most generally used form of stranding arrangement is the concentric-lay. A concentric-lay cable is composed of a single wire core about which is helically wound one or more layers of wires or strands. In the most common type of concentric-lay conductor, the wires composing the outer layers are all of one size.   Where more than one layer is wound about the core, each layer is laid in an opposite direction to its adjacent layer.  A second type of stranding arrangement is the rope-lay. The rope-lay cable consists of a concentric-lay conductor core about which is helically wound one or more layers of strands in which the strands are themselves stranded.

Copper, because of its high tensile strength when hard drawn into a wire, can be fabricated into the previously mentioned wires and types of cable without the necessity of being alloyed or combined with other metals to supplement its strength. Aluminum, however, although extremely useful as cable conductor material, depends upon steel core to supplement its strength. This combination of steel and aluminum, commonly known as ACSR, aluminum cable steel reinforced, forms a light weight cable of high strength and high electrical current carrying capacity.