SWA, PVC or XLPE ?

[T i m]

Hi All,

Just doodling .. I'm slightly confused re the terms PVC and XLPE and with specific reference to TLC's cable calculator.

you choose SWA PVC or SWA XLPE there can be quite a difference in the resultant cable size for a given load / length etc?

My best undertanding so far is the PVC bit refers to the outer and inner sheath material and XLPE the actual core conductors insulation?

So, if a cable was marked:

'Electric Cable 600/1000V BS5467 Alcatel Kablo 3x6 2000 basec'

I believe that is telling me it's a 3 core 6 sq mm (per core) armoured cable that is rated for up to 1000V and conforms to the BS5467 standard but does it tell you any more about the construction (or does the BS5467 tell us all we need to know) please?

All the best ..

T i m

[Andy Wade]

Yes, although for many SWA applications the size will be determined by voltage drop rather than current rating. Also note that to make use of the higher current rating of XLPE insulated cables all connected accessories must be suitable for the higher operating temperature of 90 deg. If in doubt use the PVC ratings, based on 70 deg.

No it's the insulation material. The sheath is PVC in both cases. PVC insulated SWA cables to BS 6346 have disappeared from the general market now, so will only be found in older installations. Anything you buy now will almost certainly by XLPE insulted to BS 5467.

1000 V between cores and 600 V to earth.

Yes, that tells you it's XLPE. 2000 is the year of manufacture and BASEC is an approval body -

All the best ..

HTH

[T i m]

Ah, so the plot thickens .. ;-)

So just so I get this right, outer sheath always (for this conversation) PCV, inner sheath (under wire armour) PVC and the insulation around each of the conductors is XLPE? The reason I mention that is because I have seen pictures where there is an extra membrane type layer over the conductors and under the inner sheath and it also seems to include 'filler strips' in the inter core spaces?

Ah, makes sense ;-)

It does indeed ... thanks very much Andy. ;-)

All the best ..

T i m

[Andy Wade]

Yes (ignoring your typo).

That's called the bedding and the material seems to vary between manufacturers. Sometimes it seems to be silicone elastomeric sort of material.

That's PVC for old cables to BS 6346 and XLPE for cables to BS 5467.

Pass. I'm familiar with the type of construction you describe, but I don't recall ever seeing that used for SWA.

You're welcome.

[T i m]

Doh!

Have a look here ...

scroll down to 6942XL and that's what I'm used to with 'generic' SWA ..?

Below that is the more fancy stuff I was talking about ..

All the best ..

T i m

[Ed Sirett]

^^^^^^^^^ Shame, 'twas a great cable before the BSI slagged it off.

[Andy Wade]

Oh, OK, larger sizes (>=25 mm^2), shaped conductors and in one case a different standard (BS 6724) with OHLS (zero halogen, low smoke) sheath material. I guess the transparent film material is there to stop the bedding layer sticking to the insulation in manufacture.

[Andy Wade]

Guilty, your honour. In mitigation I plead that you missed the "by" that should have been a "be."

Useful stuff, insulting tape...