PEL Conductor: Definition, Examples of Systems, Requirements

PEL Conductor: conductor combining the functions of both a protective earthing conductor and a line conductor [SOURCE: IEC 60050-195:2021, 195-02-14].

The designation “PEL” is formed from two short designations: protective conductor “PE” and line conductor “L”, indicating the conductors whose function is intended to be performed by a PEL conductor.

A PEL conductor, like other protective conductors, is not considered a live part. However, a PEL conductor is a current-carrying conductor that is counted in the total number of conductors of an electrical circuit, network or system.

The essence of the PEL-conductor is explained quite fully by Y.V. Kharechko in his book [2]:

« The requirements in IEC 60364-4-41:2017 [2] clause 411.4.2 for TN systems require that the neutral point or midpoint of the power source be grounded. If the neutral point or midpoint is not available or unavailable, the line conductor must be grounded. A earthed line conductor can be assigned to serve as a protective earthing conductor. In these circumstances, it will be a PEL conductor. That is, in some cases, the functions of a protective earthing conductor and a line conductor may be combined in a single conductor in an electrical installation of a building or parts thereof. This conductor is called a combined protective earth conductor and line conductor. However, it is better known by its short name “PEL conductor” or simply “PEL”. »

Examples of systems in which PEL conductors are used.

Consequently, single-phase TN-C and TN-C-S systems without neutrals may have PEL conductors (Figures 31C2 and 31B4). PEL conductors may also be present in three-phase TN-C and TN-C-S systems without neutrals, as for example shown in Figures 3 and 4.

PEL conductors can also be in DC electrical systems that correspond to TN-C (see Figure 31J), TN-S (Figure 31H) and TN-C-S (Figure 31K) types of earthing systems.

TN-C system single-phase, 2-wire with earthed phase conductor
Figure 31C2 [4] – TN-C system single-phase, 2-wire with earthed phase conductor and protective conductor functions combined in a single conductor throughout the distribution system

NOTE. Additional earthing of the PEL conductor in the distribution line and in the electrical installation may be provided.

TN-C-S system single-phase, 2-wire where the PEL conductor is separated into the protective conductor and the earthed phase conductor at the origin of the electrical installation
Figure 31B4 [4] – TN-C-S system single-phase, 2-wire where the PEL conductor is separated into the protective conductor and the earthed phase conductor at the origin of the electrical installation

NOTE. Additional earthing of the PEL conductor in the distribution line and of the protective conductor in the electrical installation may be provided.

TN-C three-phase three-wire system pel conductor
Figure 3 – TN-C three-phase three-wire system (based on figure 3 from the book [3] by author Kharechko Y.V.)
TN-C-S three-phase three-wire system with separation of PEL conductor into an earthed line conductor and protective conductor at the input of the installation
Figure 4 – TN-C-S three-phase three-wire system with separation of PEL conductor into an earthed line conductor and protective conductor at the input of the installation
figure 31J TN-C DC two-wire system pel conductor
Figure 31J [4] – TN-C DC 2-wire system
TN-S DC 2-wire system
Figure 31H [4] – TN-S DC 2-wire system
TN-C-S DC 2-wire system
Figure 31K – TN-C-S DC 2-wire system

Requirements for PEL conductors.

Because the PEL conductor has the electrical shock protection functions of a protective earthing conductor, it:

  • A PEL conductor may only be used in fixed electrical installations and, for mechanical reasons, shall have a cross-sectional area not less than 10 mm2 copper or 16 mm2 aluminium [Clause 543.4.1, 5].
  • Must comply with the requirements for the protective conductor. Above all, the continuity of the electrical circuit of the PEL conductor must be ensured. Therefore, it is forbidden to include switching devices such as fuses, circuit breakers, disconnectors, etc. in its circuit.
  • Extraneous-conductive-parts shall not be used as PEL conductor.
  • Metallic enclosures of wiring systems shall not be used as PEL conductor, except for busbar trunking systems complying with IEC 60439-2 and for powertrack systems complying with IEC 61534-1.

Flexible connection cables through which Class I portable and mobile electrical equipment is connected to fixed electrical Flexible connection cables through which Class I portable and mobile electrical equipment is connected to fixed electrical circuits of fixed electrical installations must have separate conductors that serve as protective conductors. Protective conductors of cables should be connected to PEL-, PEM-, PEN-conductors of fixed electrical circuits and to exposed conductive parts of Class I electrical equipment. Thus, in low-voltage installations corresponding to TN-C, TN-C-S types of earthing systems, the division of PEL conductors of fixed electrical circuits into line and protective conductors should be made:

  • When connecting portable and mobile electrical equipment of Class I, through flexible connection cables of any cross-section;
  • When connecting Class I fixed electrical equipment, by means of copper and aluminum conductors with a cross section of less than 10 mm2 and 16 mm2, respectively.

Color and alphanumeric identification.

A PEL conductor, when insulated, shall be identified by GREEN-AND-YELLOW coloured insulation throughout its length and with BLUE coloured markings at its terminations and points of connection of the PEL conductor [Clause 6.3.4, 6].

The BLUE coloured markings at the termination and points of connection may be omitted provided one of the following two conditions is met:

  • in electrical equipment, if relevant requirements are included in specific product standards or within a country;
  • in the case of wiring systems, for example those used in industry, if decided by the relevant committee.

If confusion with a PEN or PEM conductor is likely, the alphanumeric designation as given in 7.3.5 [6] shall be indicated at the terminations and points of connection. According to the clause [7.3.5, 6] the alphanumeric identification of a PEL conductor shall be “PEL”.

References

  1. IEC 60050-195:2021
  2. IEC 60364-4-41:2017
  3. Kharechko Y.V. Concise Terminological Dictionary of Low Voltage Electrical Installations. Part 1 // Appendix to the journal “Library of the safety engineer. – 2011. – № 3. – 160 c.
  4. IEC 60364-1
  5. IEC 60364-5-54
  6. IEC 60445-2021