Current-Carrying Conductor: Definition, Meaning, Examples

Current-carrying conductor: a conductor which carries the electric current under normal conditions [defined in the IEC TS 62257-5-2015].

Note 1 to entry: The line conductor (L), the neutral conductor (N), the mid conductor (M), the PEN conductor, the PEM conductor and the PEL conductor are the current-carrying conductors. The protective conductor (PE) is not the current-carrying conductor.

A protective conductor under normal conditions conducts almost no electric current, because there are no faults and no induced currents, such as earth-fault currents. Therefore, it is not considered a current-carrying conductor and is not included in the total number of conductors in electrical circuits, networks and systems.

Examples of Current-Carrying Conductors

The term “current-carrying conductor ” distinguishes from the totality of conductors such conductors through which, under normal conditions characterized by the absence of faults, an electric current flows.

Firstly, current-carrying conductors include live conductors such as a phase conductor (L), a pole conductor (L), the neutral conductor (N) and the mid conductor (M).

Secondly, they are PEN conductor, PEM conductor and PEL conductor, which are not live conductors but through which electric current flows under normal conditions. A protective conductor (PE) is not a current-carrying conductor because under normal conditions there is almost no electric current flowing through it.

When referring to the total number of conductors in an electrical circuit, network, or system, only the current-carrying conductors are considered. A 3-phase 4-wire AC circuit, for example, may consist of three phase conductors and a fourth neutral conductor or PEN conductor. The same electrical circuit may include three phase conductors, a neutral conductor, and a protective conductor, which is not counted in the total number of conductors.

Figures 31A1 and 31C of IEC 60364-1 (see Figures 1 and 2 of this article) illustrate these circuits.

TN-S system 3-phase, 4-wire with separate the neutral conductor and the protective conductor throughout the distribution system
Figure 1 – TN-S system 3-phase, 4-wire with separate the neutral conductor and the protective conductor throughout the distribution system
TN-C system with neutral and protective conductor functions combined in a single conductor throughout the system
Figure 2 — TN-C system with neutral and protective conductor functions combined in a single conductor throughout the system

In DC electrical systems, 2-wire electrical circuits can consist of a pole conductor and a mid conductor, a PEM conductor or a PEL conductor. 3-wire electrical circuits can consist of two pole conductors and a mid conductor, a PEM conductor or a PEL conductor. Protective conductors, even if present in electrical circuits, are not counted in the total number of conductors. Figures 3 and 4 clearly illustrate two- and three-wire DC electrical circuits.

TN-S DC 2-wire system
Figure 3 – TN-S DC two-wire system [Figure 31H1 of IEC 60364-1]
TN-S DC 3-wire system
Figure 4 – TN-S DC 3-wire system [Figure 31H1 of IEC 60364-1]

FAQ

Is Neutral a Current Carrying Conductor?

YES.