TRANSMISSION LINES CONDUCTOR DEFINITION TUTORIALS

Wire
A rod or filament of drawn or rolled metal whose length is great in comparison with the major axis of its cross section. The definition restricts the term to what would ordinarily be understood by the term solid wire.

In the definition, the word slender is used in the sense that the length is great in comparison with the diameter. If a wire is covered with insulation, it is properly called an insulated wire, while primarily the term wire refers to the metal; nevertheless, when the context shows that the wire is insulated, the term wire will be understood to include the insulation.

Conductor
A wire or combination of wires not insulated from one another, suitable for carrying an electric current. The term conductor is not to include a combination of conductors insulated from one another, which would be suitable for carrying several different electric currents.

Rolled conductors (such as bus bars) are, of course, conductors but are not considered under the terminology here given.

Stranded Conductor
A conductor composed of a group of wires, usually twisted, or any combination of groups of wires. The wires in a stranded conductor are usually twisted or braided together.

Cable
A stranded conductor (single-conductor cable) or a combination of conductors insulated from one another (multiple-conductor cable). The component conductors of the second kind of cable may be either solid or stranded, and this kind of cable may or may not have a common insulating covering.

The first kind of cable is a single conductor, while the second kind is a group of several conductors. The term cable is applied by some manufacturers to a solid wire heavily insulated and leads covered; this usage arises from the manner of the insulation, but such a conductor is not included under this definition of cable.

The term cable is a general one, and in practice, it is usually applied only to the larger sizes. A small cable is called a stranded wire or a cord, both of which are defined below.

Cables may be bare or insulated, and the latter may be armored with lead or with steel wires or bands.

Strand
One of the wires of any stranded conductor.

Stranded Wire
A group of small wires used as a single wire. A wire has been defined as a slender rod or filament of drawn metal. If such a filament is subdivided into several smaller filaments or strands and is used as a single wire, it is called stranded wire.

 There is no sharp dividing line of size between a stranded wire and a cable. If used as a wire, for example, in winding inductance coils or magnets, it is called a stranded wire and not a cable. If it is substantially insulated, it is called a cord, defined below.

Cord
A small cable, very flexible and substantially insulated to withstand wear. There is no sharp dividing line in respect to size between a cord and a cable, and likewise no sharp dividing line in respect to the character of insulation between a cord and a stranded wire.  Usually the insulation of a cord contains rubber.

Concentric Strand
A strand composed of a central core surrounded by one or more layers of helically laid wires or groups of wires.

Concentric-Lay Conductor
Conductor constructed with a central core surrounded by one or more layers of helically laid wires.

Rope-Lay Conductor
Conductor constructed of a bunch-stranded or a concentric-stranded member or members, as a central core, around which are laid one or more helical layers of such members.

N-Conductor Cable
A combination of N conductors insulated from one another. It is not intended that the name as given here actually be used. One would instead speak of a “3-conductor cable,” a “12-conductor cable,” etc. In referring to the general case, one may speak of a “multipleconductor cable.”

N-Conductor Concentric Cable
A cable composed of an insulated central conducting core with N-1 tubular-stranded conductors laid over it concentrically and separated by layers of insulation.

This kind of cable usually has only two or three conductors. Such cables are used in carrying alternating currents. The remark on the expression “N conductor” given for the preceding definition applies here also. (Additional definitions can be found in ASTM B354.)

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