SWA csa

[Frosty69]

Hi people,

I am completing some works at an oil refinery and cannot find any identification on the cable like 4x70mm etc. Can I use circumference of the individual phase (after the gland so i can see all phases) divided by pi (3.14) to get the diameter of the phase? I only ask as the cable isn't a perfect circle more like a triangle with rounded edges!

Thanks

 

[telectrix]

cut a small piece off and compare it with some known cable.

 

[Darkwood]

its not an exact science as insulation thickness varies brand to brand and also shaping as you have found, best way is to have a set of lugs in your kit and see which fits the cable core or if already lugged the lug should be stamped.

 

[Frosty69]

I won't be able to do that as the cables I need to know sizes of are sub mains so can't turn them off with the the of plant etc that they need to use.

 

[Frosty69]

All I'm thinking is if in my opinion it is 70mm but then it turns out to be 60mm but that cable isn't big enough for load etc then id be to blame, just wondered if there was any way of getting an exact size but like you say may be best if lugged.

 

[Darkwood]

sample cables are your only option really and shaped if you can, and above you looked at finding an area of a circle i.e. round core then you go on to say its triangular shaped so i would assume a more accurate sum would be the area of a triangle allowing for the insulation.

 

[Darkwood]

Cable sizing is 50mm - 70mm - 95mm as long are your area calcs hovers around 70mm you'll know its pretty good guess, so a minimum of 20mm^2 to next cable size up or down.

 

[Frosty69]

your right dark wood and I suppose if i get the calculation as near as possible then that will have to do. Thanks

 

[Darkwood]

you can always re-enforce you assumptions and do the cable calcs on length of run etc if you are aware of the fuses fitted upstream, if not see if you can clamp it while its loaded up and use judgement to establish a lesser cable should be running warm or hot carrying that load thus must be what you thought, it about using all the clues around you, usually when dist-boards are fitted their may be others wired using same cable, if so it might be possible to isolate the other cable to check the lugs, what you really need to establish here more than anything is what the front end fuses are for it as these could be a limiting factor regardless of cable size.

 

[snowhead]

This may get you closer to the size;

http://www.eland.co.uk/documents/SWA Cables - BS5467.pdf

 

[Knobhead]

The CSA can be worked out by weight / length. This is for a stripped length of conductor.

Copper	8930KG per M cube
CSA	Gm per Metre
1	8.93​
1.5	13.40​
2.5	22.33​
4	35.72​
6	53.58​
10	89.30​
16	142.88​
25	223.25​
35	312.55​
50	446.50​
70	625.10​
95	848.35​
120	1,071.60​
150	1,339.50​
195	1,741.35​
240	2,143.20​
300	2,679.00​

Aluminium
CSA	Gm
1	2.56
1.5	3.84
2.5	6.40
4	10.24
6	15.36
10	25.60
16	40.96
25	64.00
35	89.60
50	128.00
70	179.20
95	243.20
120	307.20
150	384.00
195	499.20
240	614.40
300	768.00

 

[Darkwood]

i hope the weighing scales are insulated :O/

 

[Knobhead]

It’s the most accurate method you’ll find. You can’t measure the diameter of a compressed shaped conductor.

Archimedes gave us another method. Using a measuring jar put a known amount of water in, add a known length of conductor and read off the increased volume in the jar. It’s a simple bit of maths after that.

OK I’ve always worked where I had access to laboratory equipment.

But to be honest it’s always been a case of looking at it and I’ll tell you what size it is.

 

[Darkwood]

agree and yrs of experience and i can do same but was refering to O/P mentioning he cant shut power down hence our stranger than normal suggestions ...

 

[benji]

actually the thread is quite frightening to me anyway,i mean no disrespect but the op knows nothing about cable construction yet he seems to be in a position of being able to switch