sizing SWA armour as cpc using adiabatic......

[brman]

Jesus, the times that old table rears it's ugly head!! At best this table is confusing, ...worst most of values also need calculating as many that state do not comply actually DO comply!!

Throw this table away is my advice, and use this table for SWA CPC compliance with no need for any futher calculations. This table is NOT intended for use to indicate Bonding compliance

I agree, that old table has confused me a few times in the past. I have a very similar table to you which I got from Gadsolutions website with quite a good explanation of what is all about.
Looking at it again has made me realise that I used the wrong k values (or more specifically k ratios) in my original sums but it doesn't affect the result so I will gloss over that......

That said, when looking at k values I am a bit confused by the table you quote. The minimum SWA CSA to meet 54G (54.7 in the BGB?) is the same for PVC 70[SUP]0[/SUP]C and XLPE 90[SUP]0[/SUP]C. Surely the k values of both the copper core and the steel armour are different between the two so required steel csa will be different?
Your figures match the table I have but don't match what I would expect by calculation so I am confused, especially as it does appear to affect which sizes are acceptable.

Any comments on this?

 

[Engineer54]

I agree, that old table has confused me a few times in the past. I have a very similar table to you which I got from Gadsolutions website with quite a good explanation of what is all about.
Looking at it again has made me realise that I used the wrong k values (or more specifically k ratios) in my original sums but it doesn't affect the result so I will gloss over that......

That said, when looking at k values I am a bit confused by the table you quote. The minimum SWA CSA to meet 54G (54.7 in the BGB?) is the same for PVC 70[SUP]0[/SUP]C and XLPE 90[SUP]0[/SUP]C. Surely the k values of both the copper core and the steel armour are different between the two so required steel csa will be different?
Your figures match the table I have but don't match what I would expect by calculation so I am confused, especially as it does appear to affect which sizes are acceptable.

Any comments on this?

The clue is in the title of the XLPE Table....


''Table for 90[SUP]0[/SUP]C Thermosetting SWA cables operating at 70[SUP]0[/SUP]C.''



The actual instances that you would use the 90 C capability of XLPE insulated cables is going to be extremely rare, unless working in boiler rooms or other high temperature situations where the components to which these cables are to be connected too, are also required to be rated at 90 C....

The difference in the lower CSA of the SWA on the the various sizes of 90 C, cables in the thermosetting table, is because the cores insulation thickness is much thinner than the PVC insulation, and therefore the overall dia of the cable is smaller, so less steel wires are required to surround the inner cable.... That's about it really...lol!!

 

[brman]

thanks. that does indeed explain it.

 

[Chr!s]

You need to look at the initial start Temp and the Final Temp, XLPE has a limiting temp of 250 C, if your start Temp is 60(for the Armor) C then your K Factor = 58 for Steel, XLPE copper with a start temp of 70 C and a limit of 250 C K factor = 154.

SWA can come with XLPE oversheath and PVC, the conductors though now are XLPE insulated.