schedule of inspections

[JulianC]

My interpretation is that the armour, being a conductor, cannot be an insulator or form any part of insulation. Ergo, SWA ain't reinforced/double insulated.

 

[IQ Electrical]

My interpretation is that the armour, being a conductor, cannot be an insulator or form any part of insulation. Ergo, SWA ain't reinforced/double insulated.

Not just a conductor but an EARTHED conductor, how can this comply with the criteria for class II ?

 

[JulianC]

It can't.

By definition a conductor cannot be an insulator and vice versa.

SWA offers mechanical reinforcement, not insulation reinforcement IMHO.

 

[the_mouse]

Hi, SWA reinforced insulation or not?? Well, my primary employment is cable manufacture and to achieve a certain grade we have tests on cable make up so I'll attempt to clear up some issues if i can.
The only part of a cable that is referred as insulation is the extruded material which covers the conductors, the inner extruded layer around the cores is the bedding layer, its only purpose is to protect the insulation from damage which would be caused by the steel wires during manufacture and if the cable suffered mechanical impact during service, a sort of cushion, this bedding layer is NOT subject to inline testing to ensure integrity. Next the steel wires to provide mechanical protection then finally the oversheath which provides mechanical protection, prevents moisture ingress and hold the cable all together, imagine if you cut a SWA cable with no oversheath it would fall apart, in fact some oversheaths on cables rated at 33, 66 and 132KV have a coating of graphite applied which is a very good conductor! So to answer the question is SWA reinforced insulation definitely NO, it may have three layers if insulated material but only one is actually insulation it has additional mechanical protection via the steel wire but it is not reinforced.
Think of concrete, if a concrete pillar had wire bars aplied to its outer surface it would not make reinforced but if the bars were inserted during pouring then that is makes it reinforced, in Chritpher Kitchers book, a practical guide to 17th ed wiring regs page 133 he defines reinforced insulation as a "single layer of very strong insulation"
HTH

 

[IQ Electrical]

Hi, SWA reinforced insulation or not?? Well, my primary employment is cable manufacture and to achieve a certain grade we have tests on cable make up so I'll attempt to clear up some issues if i can.
The only part of a cable that is referred as insulation is the extruded material which covers the conductors, the inner extruded layer around the cores is the bedding layer, its only purpose is to protect the insulation from damage which would be caused by the steel wires during manufacture and if the cable suffered mechanical impact during service, a sort of cushion, this bedding layer is NOT subject to inline testing to ensure integrity. Next the steel wires to provide mechanical protection then finally the oversheath which provides mechanical protection, prevents moisture ingress and hold the cable all together, imagine if you cut a SWA cable with no oversheath it would fall apart, in fact some oversheaths on cables rated at 33, 66 and 132KV have a coating of graphite applied which is a very good conductor! So to answer the question is SWA reinforced insulation definitely NO, it may have three layers if insulated material but only one is actually insulation
HTH

Thanks for that, I was pretty certain but it's nice to have some technical proof instead of interpretations of ambiguous regulations!

 

[pushrod]

Hi, SWA reinforced insulation or not?? Well, my primary employment is cable manufacture and to achieve a certain grade we have tests on cable make up so I'll attempt to clear up some issues if i can.
The only part of a cable that is referred as insulation is the extruded material which covers the conductors, the inner extruded layer around the cores is the bedding layer, its only purpose is to protect the insulation from damage which would be caused by the steel wires during manufacture and if the cable suffered mechanical impact during service, a sort of cushion, this bedding layer is NOT subject to inline testing to ensure integrity. Next the steel wires to provide mechanical protection then finally the oversheath which provides mechanical protection, prevents moisture ingress and hold the cable all together, imagine if you cut a SWA cable with no oversheath it would fall apart, in fact some oversheaths on cables rated at 33, 66 and 132KV have a coating of graphite applied which is a very good conductor! So to answer the question is SWA reinforced insulation definitely NO, it may have three layers if insulated material but only one is actually insulation it has additional mechanical protection via the steel wire but it is not reinforced.
Think of concrete, if a concrete pillar had wire bars aplied to its outer surface it would not make reinforced but if the bars were inserted during pouring then that is makes it reinforced, in Christopher Kitchers book, a practical guide to 17th ed wiring regs page 133 he defines reinforced insulation as a "single layer of very strong insulation"
HTH

Thanks mouse, brilliant response - i'll be printing out your reply