Buried SWA

[rainydays]

can anyone tell me which is the right correction/derating factor to apply to an SWA buried in the ground, in a duct at a depth of between 0.5-0.7 metres. Overhead protection is required. I keep coming across a figure of 0.9
I am aware that there are others for temperature and soil resistivity etc, it’s just the cc one that is throwing me. Much appreciated.

 

[poni]

buried in the ground, in a duct at a depth of between 0.5-0.7 metres. Overhead protection is required

can you have buried overhead cables?

would you not use this Column

 

[rainydays]

Ha ha, just seen the misspelling, I think I clicked on predictive text. It was supposed to say overload protection required. I.e. it is not a fixed load.

 

[Captain Kirk]

Remember the cpc calculation - not all SWA cables are compliant

 

[Murdoch]

Use 3 core swa is my advice

 

[Fleeting]

Use 3 core swa is my advice

Why's that then?

 

[Murdoch]

Why's that then?

Come across too many poorly or not terminated outer cores ….. so no CPC continuity - when there should be

 

[Captain Kirk]

I agree Murdoch - we are the only civilised country who still allow a non-copper cpc such as SWA.

In hazardous installations such as petrol pumps the steel armour cannot be used as the cpc. The cpc must be an internal copper core of the cable. The cable armour must be earthed at the supply end only for cable damage fault protection to prevent and fault current arcing in the hazardous area.

Its high time the SWA cable BS standard was changed to have an insulated earth core in the cable.

 

[roys]

Mmmmm, worked on Haz Area kit most of my working life, been retired for a few years now so unless things have changed in recent years we always earthed the armour at both ends, any earth missing on the plant end would be picked up on haz area inspections and remedial action would have to be taken promptly.
Agree though on using a separate core for your CPC which is what we did.