stranded and solid copper cables
stranded and solid copper cables
(OP)
usually specs require using stranded copper cables for substation applications .what is the problem with solid copper?
thanx.
thanx.
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stranded and solid copper cables
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RE: stranded and solid copper cables
RE: stranded and solid copper cables
RE: stranded and solid copper cables
RE: stranded and solid copper cables
were pulled easily but after noticing that they are solid they were ordered to be removed.
RE: stranded and solid copper cables
RE: stranded and solid copper cables
RE: stranded and solid copper cables
Most terminals in substation equipment are designed for use with stranded wire or compression lugs. Solid conductor terminations will be less reliable.
Stranded wire is also easier to work with and pull.
We typically specify solid copper wire for lighting and receptacle circuits and stranded for everything else.
RE: stranded and solid copper cables
"Larger-size conductors are required to be stranded to provide greater flexibility. This requirement does not apply to busbars and the conductors of Type MI mineral-insulated metal-sheathed cable. In addition, the bonding conductors of a common bonding grid of a permanently intalled swimming pool are required to be solid, nonstranded conductors of 8 AWG or larger, according to 680.26(C)."
RE: stranded and solid copper cables
RE: stranded and solid copper cables
-Max
RE: stranded and solid copper cables
I really don't think flexibiity is a critical factor when dealing with #12 and #10 control circuits. Stranded wire will be easier to pull, but most substation runs are pretty short.
I have seen a lot of solid control wire in very old substations, but it isn't used anymore, at least in the US.
RE: stranded and solid copper cables
-Max
RE: stranded and solid copper cables
RE: stranded and solid copper cables
Many electrical engineers have the notion that a stranded wire of same dia as a solid conductor will have less skin effect and will have a higher current carrying capacity.This is a misnomer.AC current will see the stranded wire same as a solid rod and current will tend to concentrate on outer layers.In fact skin effect will be more for stranded wire due to the stranding factor .
But all this will change once the strands are insulated from one another by an insulation say ,enamel or paper.Then skin effect is completely eliminated or reduced and still better results are obtained when the strands are transposed.This is the application in Roebel bars used in large generators and motors and Continuously Transposed Cable used in the windings of large Power transformers
RE: stranded and solid copper cables
Also, when terminating large gauge wire to terminals, we use conductive tape to hold the strands together. But the stranded often needs tightening more often than solid.
RE: stranded and solid copper cables
The NEC does not usually apply to substations. Parts of privately owned substations may, but in general the NESC and/or the whims of the local inspector cover substations. In my experience seldom does a local inspector look at a substaion, usless it's just for a tour.
Solid aluminum cable with XLP insulation is commonly used for URD system in sizes up to 2/0. It would seem that solid cable would be harder to pull but in practice it is not. The stiffness of the insulation is greater that that of the conductor so the change from stranded to solid doesn't really affect the overall stiffness.
On reason for solid conductors was water intrusion in the conductor and the "treeing" and failure of insulation.
Cable pushers work well with solid cable. It may sound strange to push a cable but it works more like installing a speedometer cable or brake cable on a bike.
RE: stranded and solid copper cables
For a fair amount of US utility and industrial switchgear, default control wiring is 14AWG/41-strand, 12AWG/65-strand, 10AWG/105-strand, etc…
RE: stranded and solid copper cables
My understanding is skin effect is higher for non insulted sranded wire because of stranding effect .When srands are insulated from one another current flows in all strands equally (an assumption wrong in many cases and hence the need for transposing )there by reducing the skin effect substantially.
RE: stranded and solid copper cables
RE: stranded and solid copper cables
RE: stranded and solid copper cables
Any control wiring installed entirely within a switchboard, that lands on the switchboard door and which crosses the door hinge should be specified to be type SIS, as defined in Article 310.13 as approved for use as "switchboard wiring only". This is a very flexible conductor which is made specifically to withstand the abuse of flexing across a door hinge.
RE: stranded and solid copper cables
RE: stranded and solid copper cables
peebee's comments are consistent with IEEE C37.20, .21 verbiage. Having to install any significant quantity of switchgear/control wiring that is not of K/H stranding would be insanity.
RE: stranded and solid copper cables
Skin effect is present to similar level in solid and stranded cable. The effect can be minimised by using special types of stranded cable in which individual strands are insulated from each other. This is known as 'Litz wire', and is used for high-frequency work in RF and in power electronics applications. At 50 / 60Hz skin effect is negligible except in exceptionally large conductors such as are found in generator bushings and gen xfmr LV bushings. The unequal distribution of current within insulated strands of a bundle is due to proximity effect, which is similar to but quite distinct from skin effect.
RE: stranded and solid copper cables
RE: stranded and solid copper cables
Being an Emergency Generator Tech I can say this after some thirty years in the field, solid wire tends to fracture do to the constant vibration after a while particularly at the terminal.
RE: stranded and solid copper cables
I agree with most of the arguments here, stranded wire is easy to install, you don't have to worry about the bends where you can break a solid wire and its easy in your fingers when you install it.
But all of that is not the point...When you're checking for a faulty wiring in an old substation where they used solid wire, pray that you don't pull a current transformer wire too hard because it will slip from the terminal and that'll be your last day...I don't know the relation between pulling stranded wire or solid wire and disconnecting it, what I do know is that we had many substations with both of them and we had a lot of problems with the ones with solid wire so we forbade the engineer department to approve the use of solid wire in any new substation due to personal safety.
I hope this usefull to you.
RE: stranded and solid copper cables