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Cables in ducts underground

Apostolos

Good morning

I always thought that if you are installing cables underground (e.g. for external lighting, Vehicles Chargers, submains to another building etc) you always use SWA cables because this offers mechanical protection.

Is this coming from a specific regulation though?

Because I have someone saying I could use double insulated cables in the underground ducts if its a short run.

However this feels odd.

Is there any regulation that I can refer to?

Sorry for the ignorance

Cheers

Parents

  • Unarmoured cables in 750N dual-walled ducts ('twin wall') to BS EN 61386-24 should be OK

    It does depend on the situation though - I reckon twinwall wouldn't prevent penetration by a simple garden fork - so I wouldn't want want to rely on it say if shallow buried in garden for example. In more controlled or benign environments it might be fine though.

    The big advantage of SWA etc is not so much the mechanical protection provided by the armour (a garden fork can pierce that relatively easily too)  - but the fact that the armour is Earthed - so anything conductive (digging tool, JCB bucket, tent peg or whatever) that penetrates through to a live core will almost certainly cause a short to the armour and so trigger automatic disconnection of supply. Same with concentric DNO cables where the concentric outer conductor is relatively soft copper rather than steel - it's the Earthing rather than mechanical protection that's relied on.

       - Andy.

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  • Unarmoured cables in 750N dual-walled ducts ('twin wall') to BS EN 61386-24 should be OK

    It does depend on the situation though - I reckon twinwall wouldn't prevent penetration by a simple garden fork - so I wouldn't want want to rely on it say if shallow buried in garden for example. In more controlled or benign environments it might be fine though.

    The big advantage of SWA etc is not so much the mechanical protection provided by the armour (a garden fork can pierce that relatively easily too)  - but the fact that the armour is Earthed - so anything conductive (digging tool, JCB bucket, tent peg or whatever) that penetrates through to a live core will almost certainly cause a short to the armour and so trigger automatic disconnection of supply. Same with concentric DNO cables where the concentric outer conductor is relatively soft copper rather than steel - it's the Earthing rather than mechanical protection that's relied on.

       - Andy.

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