multi strand 2.5mm T&E - is it OK to use?

[davesparks]

As a 'newbie' just out of interest why do you old schoolers prefer stranded? I prefer solid hands down!

You haven't encountered solid singles yet then! what a brilliant idea that was from yesteryear, can't think why it didn't catch on!

 

[Eddiesparks]

Haha yes of course i 've worked with it but terminating stranded always is a hassle and a struggle when trying to put a few in one terminal. Not to mention that you cant use my beloved push in wago connectors with the stuff !!! ;-)

 

[davesparks]

Why not? Standard push fit wago's are for use with solid and coarse stranded cable. They wouldn't be making the for 4 and 6 mm otherwise!

 

[Eddiesparks]

Oh ok so we're talking coarse like the old 7/029 stuff. Yeah i see what you mean. When i think stranded i think flex. Yuck!

 

[Engineer54]

As a 'newbie' just out of interest why do you old schoolers prefer stranded? I prefer solid hands down!

Because there is no comparison between stranded and solid core, None!! A stranded conductor is the absolute winner over a solid core conductor every single time, far more flexible and because they have a larger surface area, a higher CCC!!

Why is terminating a 3 or 7 strand cable difficult FFS, ...it's also going to be a far more secure termination into wall accessory plates and protective devices than solid core.

 

[davesparks]

Maybe I'm being daft but how does a stranded conductor have a higher ccc when compared to solid? Assuming they have the same csa and insulation etc.

 

[jaypp]

edited

 

[Engineer54]

Maybe I'm being daft but how does a stranded conductor have a higher ccc when compared to solid? Assuming they have the same csa and insulation etc.

It has a greater surface area than a solid conductor, Current tends to skim along the surface of conductors rather than through the conductor. Same principle for say Tri-rated or welding fine multi stranded cable having a far higher CCC per CSA than a standard cable...

 

[davesparks]

Ok, correct me if I'm wrong but I thought the skin depth at 50hz was approximately 8mm, therefore the skin effect was negligable for conductors less than 16mm in diameter.

 

[Engineer54]

To be totally honest i can't really recall, but current will always tend to try and stay around the surfaces of conductors. So a conductor made up of several strands (greater surface area) will carry a given current more efficiently. Don't get me wrong, i'm not saying the greater CCC is going to be significant for smaller conductor sizes, it won't but it will still hold true...

 

[Knobhead]

Maybe I'm being daft but how does a stranded conductor have a higher ccc when compared to solid? Assuming they have the same csa and insulation etc.

Look up “skin effect” on the tinterweb.

Basically with AC most of the current density is carried toward the surface of the conductor, the density decreases towards the centre. Divide the conductor in to multiple strands and the surface area increases and therefore the current capacity for the same CSA.

Just to chuck a spanner in the works. With DC the current density is uniform throughout the conductor. This is why HVDC is being adopted for bulk transmission. DC also stops reflected frequencies over long distances.

Doesn’t everyone know this? :smilielol5:

 

[davesparks]

See my next post after that, skin depth at 50hz is approx 8mm

 

[Knobhead]

There’s no set depth, its proportional. It really only comes in to play with larger CSA conductors. But the principle holds throughout.

I got interested in it when installing and modifying switchboards and came across tubular busbars.
One board I came across regularly had 4000A through the bars and muggin’s (me) was asked to install an inline ACB. We had some 8x⅜” from the original install. I didn’t fancy bending that so I went for 4 x 2½x¼“ laminated bars, they ran cooler.

 

[Engineer54]

There’s no set depth, its proportional. It really only comes in to play with larger CSA conductors. But the principle holds throughout.

I got interested in it when installing and modifying switchboards and came across tubular busbars.
One board I came across regularly had 4000A through the bars and muggin’s (me) was asked to install an inline ACB. We had some 8x⅜” from the original install. I didn’t fancy bending that so I went for 4 x 2½x¼“ laminated bars, they ran cooler.

Our LG fabricated Schneider 3.8KA MV Switchboards have insulated tubular bus bars...

 

[davesparks]

That's why I said approximately 8mm deep. It obviously varies with frequency, the higher the frequency the thinner the skin.

I had a bit of a row on a landrover forum about this. Someone was convinced that the bit of lightening conductor I've used for the battery negative in my landrover would be ineffective due to the skin effect meaning you have to use fine stranded cable for DC.