Isolation of the neutral conductor: Difference between revisions
From Electrical Installation Guide
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{{Menu_Sizing_and_protection_of_conductors}} | {{Menu_Sizing_and_protection_of_conductors}} | ||
[[File:DB422336. | [[File:DB422336.png]] | ||
(see {{FigRef|G64}}) | (see {{FigRef|G64}}) | ||
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| Single-phase | | Single-phase | ||
(Phase-Neutral) | (Phase-Neutral) | ||
| [[File:DB422337. | | [[File:DB422337.png]] | ||
'''or''' <br> | '''or''' <br> | ||
[[File:DB422340. | [[File:DB422340.png]] | ||
| [[File:DB422338. | | [[File:DB422338.png]] | ||
| [[File:DB422337. | | [[File:DB422337.png]] | ||
| [[File:DB422339. | | [[File:DB422339.png]]{{TabRef|Tab1222|b}} | ||
'''or''' <br> | '''or''' <br> | ||
[[File:DB422337. | [[File:DB422337.png]] | ||
|- | |- | ||
| Single-phase | | Single-phase | ||
(Phase-Phase) | (Phase-Phase) | ||
| [[File:DB422344. | | [[File:DB422344.png]]{{TabRef|Tab1222|a}} | ||
'''or''' <br> | '''or''' <br> | ||
[[File:DB422345. | [[File:DB422345.png]] | ||
| [[File:DB422345. | | [[File:DB422345.png]] | ||
| [[File:DB422344. | | [[File:DB422344.png]]{{TabRef|Tab1222|a}} | ||
'''or''' <br> | '''or''' <br> | ||
[[File:DB422345. | [[File:DB422345.png]] | ||
| [[File:DB422345. | | [[File:DB422345.png]] | ||
|- | |- | ||
| Three-phase four wires | | Three-phase four wires | ||
Sn ≥ Sph | Sn ≥ Sph | ||
| [[File:DB422341. | | [[File:DB422341.png]] | ||
| [[File:DB422342. | | [[File:DB422342.png]] | ||
| [[File:DB422341. | | [[File:DB422341.png]]{{TabRef|Tab1222|c}} | ||
| [[File:DB422343. | | [[File:DB422343.png]]{{TabRef|Tab1222|b}} | ||
'''or''' <br> | '''or''' <br> | ||
[[File:DB422341. | [[File:DB422341.png]] | ||
|- | |- | ||
| Three-phase four wires Sn < Sph | | Three-phase four wires Sn < Sph | ||
| [[File:DB422343. | | [[File:DB422343.png]] | ||
| | | | ||
| [[File:DB422343. | | [[File:DB422343.png]] | ||
| [[File:DB422343. | | [[File:DB422343.png]]{{TabRef|Tab1222|b}} | ||
'''or'''<br> | '''or'''<br> | ||
[[File:DB422341. | [[File:DB422341.png]] | ||
|- | |- | ||
{{TableEnd|Tab1222|G64|The various situations in which the neutral conductor may appear | {{TableEnd|Tab1222|G64|The various situations in which the neutral conductor may appear | ||
Revision as of 20:42, 5 May 2018
(see Fig. G64)
It is considered to be the good practice that every circuit be provided with the means for its isolation.
| TT | TN-C | TN-S | IT | |
|---|---|---|---|---|
| Single-phase
(Phase-Neutral) |
or |
|
|
 [b]
or |
| Single-phase
(Phase-Phase) |
 [a]
or |
|
[a]
or |
|
| Three-phase four wires
Sn ≥ Sph |
|
|
[c]
|
 [b]
or |
| Three-phase four wires Sn < Sph |
|
|
[b]
or |
[a] Authorized for TT or TN-S systems if a RCD is installed at the origin of the circuit or upstream of it, and if no artificial neutral is distributed downstream of its location
[b] The neutral overcurrent protection is not necessary:
- If the neutral conductor is protected against short-circuits by a device placed upstream, or,
- If the circuit is protected by a RCD which sensitivity is less than 15% of the neutral admissible current.
[c] In some coutries the rules applied for TN-S are the same than the rules for TN-C
Fig. G64 – The various situations in which the neutral conductor may appear
