Zero sequence impedance of cable

[JakeLong]

I'm trying to calculate the zero sequence impedance of a cable for the calculation of single phase to ground fault and could use some clarification.

The cable in question is 3x300/25mm² NA2XS2Y 6/10(12)kV, which there will be installed two of in parallel along with a 35mm² PE conductor.

Is it right to assume Z0 = Z1 + 3*Ze, where Ze is only the impedance of the PE conductor. Or should the impedances of the metallic screen and earth be included in the calculation, as a parallel impedance?

 

[7anoter4]

See attached ABB tables from ABB Switchgear Manual vol.3 11 Edition

 

[7anoter4]

For Zo sequence

 

[wcaseyharman]

When I was modeling a system recently the cable had a specification sheet that included Zo.

 

[JakeLong]

@wcaseyharman unfortunately this is not the case here, but the document @7anoter4 linked does say it is better to consult with the cable manufacturer on this matter, which I will give a go. Thanks for your answers.

Though if they give me the Z0-value of the cable, won't this value only apply to the shield and earth values? How should the impedance of the PE conductor then be modeled into the Z0-value?

 

[7anoter4]

The calculation is sophisticated , indeed. You may give a glance in this article:
FUNDAMENTALS OF CALCULATION OF EARTH POTENTIAL RISE IN THE UNDERGROUND POWER DISTRIBUTION CABLE NETWORK
BY Ashok Parsotam
chapter 3.3