harmonic in power cable

[mokhzaini]

hye people..

i am currently doing my MA in electrical and my research covers harmonic in power cable. recently I browsed and found that high current actually causing the heat dissipation and power losses, which is actually quite common. But two things really interest me a lot - the skin effect and proximity effect. I understand that skin effect is caused by the high density of current flowing nearer to the conductor surface, causing heat dissipation. what i can really understand is the proximity effect. My idea is the conductors are place in very near to each other. Anyone?

 

[charlie b]

I do not recall having seen the phrase "proximity effect" before. So I have no facts to offer you. I can say, however, that between any two pieces of conductive material in the entire universe, there is mutual capacitance and mutual inductance. The closer they are to each other, the higher the impact they have on one another. Two current-carrying conductors in close proximity will each impose a magnetic field on the other. This will influence the total impedance, as seen by the source of voltage that is driving current through each of the two wires. A higher net impedance will result in more heating in the conductor.

Very general, I know. But is this the sort of information you were looking for? If so, then perhaps another Forum member can provide more details.

 

[zog]

Do you mean inductive coupling?

 

[mokhzaini]

the effects of harmonics

the effects of harmonics

well, the Mod input gimme a little idea how electrical cable can burst and burnt by the overload of current. my project involved analysis about overloading (current) in neutral cable due to harmonic, with the emphasis on how effect on the conductor (physically). i must say, the skin effect in the conductor produce excessive heating and that leads to cable bursting.

 

[bob]

well, the Mod input gimme a little idea how electrical cable can burst and burnt by the overload of current. my project involved analysis about overloading (current) in neutral cable due to harmonic, with the emphasis on how effect on the conductor (physically). i must say, the skin effect in the conductor produce excessive heating and that leads to cable bursting.

The skin effect on conductors is taken into account in NEC table 310.16 Cable Ampacity and therefore would not cause a heating problem for the standard 60 cps power. However, harmonics are not included in the table and can and do cause heating of cables.
I think the term "proximity effect" you use is concerning the relative physical location of conductors in conduits. That problem is addressed in NEC table
310.15(B)(2)(a) and when applied correctly covers the "proximity effect".

 

[mokhzaini]

oowwhwhh..

oowwhwhh..

oowwhh..

bob, are u saying skin effect do not related to harmonic at all? but then, the outer layer of conductor become heated as the current tends to flow nearer to the surface. or, simply, the harmonic will not cause such breakdown?

yes, maybe proximity effect has something to do with the location and how the conductors being installed. anyway bob, thanks alot! really appreciate ur view. thanks again

 

[bob]

oowwhh..

bob, are u saying skin effect do not related to harmonic at all? but then, the outer layer of conductor become heated as the current tends to flow nearer to the surface. or, simply, the harmonic will not cause such breakdown?

I did not say that. Skin effect is due to using AC operating frequency.
Look in some of the cable mfg catalogs and you will see that the DC resistance and the AC resistance is different. It is not significant for smaller conductors but increases and the conductor size increases.