Minimum depth underground cable

[JohnW2]

Well, yes but not with regard to the exam in question.

Indeed -but what I meant was that (in my opinion) it makes that type of exam even 'worse'.

I suppose there is no depth that would cover all situations - "shall be at a sufficient depth to avoid being damaged by any reasonably foreseeable disturbance of the ground" ... is what it states.

Sure, there obviously is no universally correct (numerical) answer. However, that doesn't alter the fact that to be competent in practice, a person needs to have enough understanding, intelligence and common sense to be able to make a (inevitably 'numerical') reasonable decision as to how deeply to bury the cable in any particular situation they encounter.

Kind Regards, John

 

[Jackrae]

Classic highlighting of the problem with multi-choice rather than written questions. You study for the exam such that you endeavour to remember the 'correct' answers. But nowhere does this imply you actually understand the subject such that you are sufficiently knowledgable about the subject a couple of weeks after having sat the exam. I've recently studied for a 3-part multichoice examination certificates in a related subject and passed each with good marks. But I know full-well that my knowledge of the subject is far from comprehensive and, as the days go by, my knoweldge diminishes. ie I studied to sit the exam and get the ticket !!

 

[oldbutnotdead]

Can't remember where I read it but sure there was something about having a hard layer in the trench as well as marker tape. When I did a run up the garden dropped ducting, water and SWA in sand, warning tape, covered in lots more sand, warning tape, bit of backfill, layer of bricks, big bits of paving slab etc, more warning tape then soil infill.
Can remember years ago putting a fence up round a bus depot in Port Talbot. We were digging post holes and found a concrete slab at about a foot down. Dug round it to get it out, on the hidden face it said ELECTRICITY. So we got the local leccy board out- there was an 11kv line just below it, just as well we didn't just smack the steel post in with the digger bucket

 

[JohnW2]

Can't remember where I read it but sure there was something about having a hard layer in the trench as well as marker tape.

Whilst there is clearly something to be said for a 'hard' layer above the cable, I don't think that there is any 'requirement' anywhere, and doubt that many people do it (at least for LV).

In fact, given that the discussion has been about SWA, I think that if it is adequately 'mechanically protected' (e.g. by concrete) it probably does not (per BS7671) have to be SWA (or have an external earthed covering of any sort), does it?

Kind Regards, John

 

[SUNRAY]

Can't remember where I read it but sure there was something about having a hard layer in the trench as well as marker tape. When I did a run up the garden dropped ducting, water and SWA in sand, warning tape, covered in lots more sand, warning tape, bit of backfill, layer of bricks, big bits of paving slab etc, more warning tape then soil infill.
Can remember years ago putting a fence up round a bus depot in Port Talbot. We were digging post holes and found a concrete slab at about a foot down. Dug round it to get it out, on the hidden face it said ELECTRICITY. So we got the local leccy board out- there was an 11kv line just below it, just as well we didn't just smack the steel post in with the digger bucket

I was working at a school and the power went off... there were 2 guys installing a new sign and found a HV cable, which due to landscaping was very few inches deep, with their all steel fencing spadehandle.