Isolation of the neutral conductor: Difference between revisions
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Revision as of 17:50, 20 December 2019
(see Fig. G68)
It is considered to be the good practice that every circuit be provided with the means for its isolation.
Fig. G68 – The various situations in which the neutral conductor may appear
| TT | TN-C | TN-S | IT | |
|---|---|---|---|---|
| Single-phase
(Phase-Neutral) |
or |
|
|
 [a]
or |
| Single-phase
(Phase-Phase) |
 [b]
or |
|
[b]
or |
|
| Three-phase four wires
Sn ≥ Sph |
|
|
[c]
|
 [a]
or |
| Three-phase four wires Sn < Sph |
|
|
[a]
or |
- - 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.
- ^ 1 2 3 The neutral overcurrent protection is not necessary:
- ^ 1 2 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
- ^ In some coutries the rules applied for TN-S are the same as the rules for TN-C
