Earthed line conductor (identification: LE): line conductor which has an electrical connection with a local earth (this term is defined in the IEC TS 62257-5-2015).
The earthed line conductors are used in single-phase 2-wire AC electrical systems, in three-phase 3-wire AC electrical systems without the neutral and in 2-wire DC electrical systems.
Examples.
In single-phase TN-S (see Figure 31A4), TN-C-S (Figure 31B4) and TT (Figure 31F3) electrical systems without neutrals, there may be earthed line (phase) conductors.



Earthed phase conductors can also be in TN-S, TN-C-S and TT three-phase electrical systems whose power supplies have no neutrals. For example, Figure 31A2 shows a TN-S system in which the phase conductor LE3 is earthed. The three-phase TN-C-S and TT systems with earthed phase conductors LE3 are shown in figures 1 и 2.



Two-wire TN-S, TN-C-S, and TT DC electrical systems use earthed pole conductors that are connected to the earthed poles of the power supplies. Figures 31K, 31L, and 31H show examples of electrical systems in which the negative pole conductor L- is earthed.



Color and alphanumeric identification requirements.
In the Russian Federation, the preferred colour of the earthed phase conductor is BLUE. If confusion with the neutral conductor, the mid conductor or the earthed pole conductor is likely, the alphanumeric designation shall be indicated at the terminations of the earthed phase conductors and in points of their connections. The alphanumeric identification of the earthed phase conductor of a single-phase electrical circuit shall be “LE”, and of a three-phase electrical circuit shall be “LE1 “, “LE2” or “LE3” [Annex B, 3].
In the Russian Federation, the preferred colour of the earthed pole conductor is 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. The alphanumeric identification of the earthed positive pole conductor shall be “LE+”, the earthed negative pole conductor shall be “LE–” [Annex B, 3].
NOTE. Terms “phase conductor” and “pole conductor” are used for the identification of line conductors in AC systems and DC systems, respectively.
References
- IEC 60364-1
- 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. Personal English translation by the author of this article.
- IEC 60445-2021