Zs

[kduck]

Hi,

what is Zs I no it is the earth fault loop impedance, but what are we measuring.

 

[Des 56]

It is the path that faults would take from the phase of the supply transformer to the installation location,thro the circuit to the fault, down the cpc to the installation main earth terminal and back to the earthed star point of the supply transformer

Therefore ZS = ZE+R1+R2

ZS is the measurement of the Whole of the fault path
ZE is the measurement of the external section
R1+R2 measurement of the circuit of the installation

The Zs then has to be low enough to allow sufficient current to flow in order for the protective device to operate in the required time

 

[DanBrown]

It is the path that faults would take from the phase of the supply transformer to the installation location,thro the circuit to the fault, down the cpc to the installation main earth terminal and back to the earthed star point of the supply transformer

Therefore ZS = ZE+R1+R2

ZS is the measurement of the Whole of the fault path
ZE is the measurement of the external section
R1+R2 measurement of the circuit of the installation

The Zs then has to be low enough to allow sufficient current to flow in order for the protective device to operate in the required time

Zs = Ze + (R1 + R2)

 

[sivoodoo]

We are measuring reistance in ohms, the lower the better, less resistance.