Pole Conductor (L): What It Is, Definition, Cross-sectional Requirements

In this article we will look at what a pole conductor is, what it is and what the requirements are for it.

Pole Conductor Definition and Meaning

Pole Conductor (L): line conductor which is used in an DC electrical circuit [defined in the IEC 60445-2021].

The term “pole conductor” is not recommended by the IEC (IEC 60050-195 and IEC 60050-826). Instead, the International Electrotechnical Vocabulary (IEV) however, the term “pole conductor” is used in the requirements and recommendations of IEC standards and other documents. Moreover, the IEV has defined the terms “mid-point conductor” and PEM conductor, which describe conductors used in DC circuits, electrical installations and systems. Therefore, along with the general term “line conductor”, the IEV should define the particular term “pole conductor”, which characterizes a line conductor to be used exclusively in DC circuits.

In requirements and recommendations relating to both AC and DC circuits, the general term “line conductor” should be used.

The pole conductor is a special case of a line conductor used in a DC electrical circuit. The pole conductors, together with the mid-point conductors and PEM conductors, are used in electrical installations of buildings to provide electrical power to the DC electrical equipment used in them.

Pole conductors are referred to as live parts. Under normal conditions, a pole conductor in a two-wire electrical circuit is normally at 220 V with regarding to the other pole conductor, and in a 3-wire electrical circuit with regard to the mid-point conductor or PEM conductor. The voltage between the pole conductors in a 3-wire electrical circuit is usually 440V.

A pole conductor is a current-carrying conductor that is counted in the total number of conductors used in an electrical circuit, network, or system.

Pole Conductor Examples

Figure 1 shows the basic combinations of pole, mid-point (M), and PEM conductors in two- and three-wire DC electrical systems.

Pole conductors
Figure 1. Basic combinations of pole, mid-point and PEM conductors (based on Figures 6 and 7 from IEC 60364-1-2005) [3]

NOTE. PEM and PEL conductors are not live conductors although they carry operating current. Therefore, the designation 2-wire arrangement or 3-wire arrangement applies.

Figure 31J – TN-C d.c. system
Figure 31J – TN-C d.c. system (the figure shows the L+ and L- pole conductors) [3]

Cross-Sectional Requirements

The minimum cross-sectional areas of pole conductors are specified in IEC 60364-5-52:2009, the same as those of line conductors (see table below). Pole conductors must be protected against overcurrent in the same way as line conductors.

Table 52.2 of IEC 60364-5-52-2009 (Minimum cross-sectional area of conductors)
Type of wiring system Use of the circuit Conductor
Material Cross-sectional area, mm2
Fixed Installations Cables and insulated conductors Power and lighting circuits Copper 1,5
Aluminium To align with cable standard IEC 60228 (10 mm2) (see note 1)
Signalling and control circuits Copper 0,5 (see note 2)
Bare conductors Power circuits Copper 10
Aluminium 16
Signalling and control circuits Copper 4
Connections with flexible insulated conductors and cables For a specific appliance Copper As specified in the relevant IEC standard
For any other application 0,75a
Extra-low voltage circuits for special applications 0,75

NOTE 1. Connectors used to terminate aluminium conductors should be tested and approved for this specific use.

NOTE 2. In signalling and control circuits intended for electronic equipment a minimum cross-sectional area of 0,1 mm2 is permitted.

NOTE 3. For special requirements for ELV lighting see IEC 60364-7-715.

NOTE 4. In the UK, 1,0 mm2 cable is allowed for use in lighting circuits.

NOTE 5. In the UK 1,0 mm2 copper cable is allowed for fixed installations utilizing cables and insulated conductors for power and lighting circuits.

a In multi-core flexible cables containing 7 or more cores, NOTE 2 applies.

Identification by Colours

Pole conductors shall be identified by the colour:

  • RED for the positive line conductor,
  • WHITE for the negative line conductor.

When the two-wire DC electric circuit is branched from a three-wire DC electric circuit, the colour identification of the pole conductor of the two-wire electric circuit should coincide with the colour identification of that pole conductor of the three-wire electric circuit to which it is connected electrically.
The earthed pole conductor shall be identified by BLUE. If confusion with the neutral conductor, the mid conductor or the earthed phase conductor is likely, the alphanumeric designation shall be indicated at the terminations of the earthed pole conductors and in points of their connections.

In the Russian Federation, the preferred colour of the positive pole conductor is BROWN, the preferred colour of the negative pole conductor is GREY.

Identification by Alphanumeric Notation

The alphanumeric identification of a pole conductor shall start with the letter “L” suffixed by:

  • in DC systems, with the sign “+” (PLUS SIGN) for the positive line conductor and with the sign “-” (MINUS SIGN) for the negative line conductor.

If no more than one line conductor is used, the suffix L may be omitted.

In the Russian Federation , the alphanumeric identification of the positive pole conductor shall be “L +” , and of the negative pole conductor shall be “L-“. When the two-wire DC electric circuit is branched from a three-wire DC electric circuit, the alphanumeric identification of the pole conductor of the two-wire electric circuit should coincide with the alphanumeric identification of that pole conductor of the three-wire electric circuit to which it is connected electrically.

Pole Conductor color and alphanumeric identification

References

  1. IEC 60445-2021
  2. IEC 60364-5-52:2009
  3. IEC 60364-1