Earth Fault Impedence

[ban-all-sheds]

Neither - you shall have to use an electrician.

 

[Loyal1]

That is what I want to know that what will the electrician do in this situation?

 

[Spark123]

The electrician will probably consult the manufacturers data for the MCCB

 

[LoveRocket]

Son, you're a long way from home.

You're not talking about changing a lightswitch here, you're talking about 300A moulded breakers - this is serious stuff, leave it to the big boys.

 

[mipax]

From link :

http://www.electrical-installation....ontact#Protection_by_means_of_circuit-breaker

Protection by means of circuit-breaker

If the protection is to be provided by a circuit-breaker, it is sufficient to verify that the fault current will always exceed the current-setting level of the instantaneous or short-time delay tripping unit (Im)

The instantaneous trip unit of a circuit-breaker will eliminate a short-circuit to earth in less than 0.1 second.
In consequence, automatic disconnection within the maximum allowable time will always be assured, since all types of trip unit, magnetic or electronic, instantaneous or slightly retarded, are suitable: Ia = Im.

Fault loop impedance must be : ZS<230(V) / Im(A)

Im - depend of type (B, C, D) or setting of circuits braker.

Setting of braker may be:

Io (factor)
Ir (factor)
Im (factor)

Io(A) = In(A) * Io (factor)
Ir(A) = Io(A) * Ir (factor)
Im(A) = Ir(A) * Im (factor)

Fault loop impedance Zs can be calculated for high current or measured.