7.12 Alternative supplies

[GCE]

They say the N and E shall (i think its a shall)be joined on the supplier side only so if that's the case for not perm joining the inveter output N to E I think they must rethink or at least I must be taught why it must be so.



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Basically ,only the supplier may earth the neutral - You can become the supplier on the load side of a generator or inverter .

6.1.6 The neutral conductor shall not be connected direct to earth or to the
earth continuity conductor on the load side of the point of control except as
allowed in 7.16.4.

You will see that this is also stipulated in municipal bylaws and Eskom bylaws since the day dot.

The reason behind the reg is to prevent fires and I will take an extreme case as an example.

My house is fed from the municipal cable network and I take 80 Amp single phase supply.The neutral is earthed at the substation transformer, 800KVA
If I then install an inverter and bridge my inverter neutral to earth with a 6sqmm or 4sqmm wire as the inverter is only 1KVA, and that inverter neutral is direct connection to municipal neutral.

If for some reason the municipal earthed/neutral comes loose or is stolen my house neutral/earth now becomes the earth/neutral for the 800KVA transformer and all imbalanced load will flow through my 16sqmm mains cable and then through my 4sqmm neutral to my inverter which is earthed
That 4sqmm wire could be in my roof space , overheat due to the current flow and cause a fire .
That earth neutral current flow could be as high as 200Amp on an imbalanced load.

That is the though process for that particular regulation

[Dylboy]

Basically ,only the supplier may earth the neutral - You can become the supplier on the load side of a generator or inverter .

6.1.6 The neutral conductor shall not be connected direct to earth or to the
earth continuity conductor on the load side of the point of control except as
allowed in 7.16.4.

You will see that this is also stipulated in municipal bylaws and Eskom bylaws since the day dot.

The reason behind the reg is to prevent fires and I will take an extreme case as an example.

My house is fed from the municipal cable network and I take 80 Amp single phase supply.The neutral is earthed at the substation transformer, 800KVA
If I then install an inverter and bridge my inverter neutral to earth with a 6sqmm or 4sqmm wire as the inverter is only 1KVA, and that inverter neutral is direct connection to municipal neutral.

If for some reason the municipal earthed/neutral comes loose or is stolen my house neutral/earth now becomes the earth/neutral for the 800KVA transformer and all imbalanced load will flow through my 16sqmm mains cable and then through my 4sqmm neutral to my inverter which is earthed
That 4sqmm wire could be in my roof space , overheat due to the current flow and cause a fire .
That earth neutral current flow could be as high as 200Amp on an imbalanced load.

That is the though process for that particular regulation

That makes all the sense! Thank you for taking the time to explain! I should have thought of the PEN fault. I really appreciate it !

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