Seven stranded conductor conundrum

La Poste · Feb 12, 2012

Greetings.

I am trying to figure out a certain size of cable that has seven strands on line, neutral and CPC respectively.
It has red and black insulation on line and neutral conductors, the CPC is coloured green (I think but am not sure yet), it is steel wire armoured.

I have found this table:

[ElectriciansForums.net] Seven stranded conductor conundrum

The table if from this link (page 121)
http://www.prysmian.com.au/export/s...df/PC350_Prysmian_TechCableGuide_2010_Web.pdf
As you can see there are seven stranded conductors in metric and imperial sizes.

I am not sure if it is metric or imperial, can anyone offer any advice on how to determine what type of cable it is.

Even if the cable is metric there are three different sizes, 7/0.67, 7/0.85, 7/1.04

I have a micrometer and I guess I could use it on each strand but this subject of older cables is a bit of a mystery to me.

Any advice on determining which sort of cable this is or any handy methods of identifying conductor sizes would be most welcome, I mean how can you tell if it is a (metric) 7/.67 or a 7/.85 or (imperial) 7/.029

Thanks.

Richard Burns · Feb 12, 2012

Generally in the UK (noticing you are using an Australian link) metric cables are solid core at the sizes you are discussing. Though I think standard imperial T&E cable usually had 3 strand CPC. The green earth / cpc is about 1950/60, I think.
If you are looking at an installation you should be able to gauge roughly the age of the installation to give you an idea of metric or imperial.
If you have metric equivalent example lengths then you can compare the size to your known values and estimate which it must be.
e.g. if you have a black and red stranded cable and it is a bit bigger (in the core, watch out for thicker insulation) than a 2.5mm metric then it will be a 7/029 cable.

Engineer54 · Feb 12, 2012

If it looks like a 2-5mm conductor size, it will be 7/029 or if like a 4mm, then it'll be 7/036, if it looks like a 6mm cable it'll be 7/044. The only sure way is to get you micrometer out and measure one of the strands. Green earth insulation indicates an old imperial cable. All those old imperial cables have better current carrying capacities than the nearest metric equivalents that replaced them...