Steel Wire Braided cable

[Engineer54]

Originally Posted by Engineer54
I'm with Darkwood 100% on this one!! But as Spoon quite rightly points out, that it's more about money/costs than any other factor!!

Does that mean some electricians in this situation, for cost reasons, would still do the job as is even if the sy cable wasn't installed properly - buried cable with no ducting or poor condition ends or unearthed braiding etc? Wouldn't that be dangerous? Or did I read your post wrong? Makes me curious what my boss will do in that case.

I would like to think that qualified and knowledgeable electricians wouldn't entertain using this SY cable in an external environment that you have described. As has been stated, the cable is totally unsuitable for these environmental conditions, especially from the mechanical protection it offers and to it's lack of UV protection!!!

 

[Deleted member 9648]

I thought it was exposed conductive parts that needed earthing. I wouldn't have considered this exposed as it's got insulation around it. So it needs earthing because it's a conductive part of the installation that could become live under fault conditions. It has no relation to induced voltages, which I was thinking could be possible from my memory of theory a while ago?

To help me try and understand at a deeper level from my current understanding of earthing, what's the likely dangers from this braid not being earthed? if it's buried, what dangerous situations could occur from this, especially if it's not buried in areas where digging would usually take place? It's easy to think of the dangers that can occur from exposed conductive parts not being earthed inside a property or at accessories, but I'm struggling to think of examples in this situation. Is it if it becomes live under fault conditions and then a person or animal cuts through the outer sheath, they get a shock - but then wouldn't the rcd trip and protect them? Is it something else?

An exposed conductive part is simply defined as a conductive part which can be touched.....on an SY cable it would be almost impossible to completely remove the possibility of touching the braid or a gland at terminations. Same principle as a flush metal backbox.

 

[davethsparky]

OP

I think you'll find there is a line in the book that requires buried cables to have an earthed metallic screen or armour, that might just be a good reason why you'd have to earth the screen!

 

[Spoon]

I think you'll find there is a line in the book that requires buried cables to have an earthed metallic screen or armour, that might just be a good reason why you'd have to earth the screen!

Do you mean 522.8.10

 

[telectrix]

the main point of earthing the armour/metallic braid/whatever is so that if the cable were to be penetrated by nail/screw.spade/whatever and said penetrating metal object was to contact with the "Live" conductor, it would also be in contact with the earthed shield and therefore cause operation of the OCPD. if it's not earthed you end up with a live armour and tool. not the best scenario.

 

[Maxstone89]

Way to confusing. Start again cheaper in the long run and safer.