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Anonymous Poster

cable resistance and impedance

01/23/2008 4:59 PM

Hey guys I am learning a new stuff on cable, could some one help me that if I know the resistance and reactance of a cable for positive, negative and zero sequence: let us say resistance 2 ohm/km and reactance 1 ohm per km, then could we convert linearly that resistance per m = 2/1000 =0.002 and reactance per m = 1/1000 = .001

or is there some other detailed conversion formula needed.

Thanks

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#1

Re: cable resistance and impedance

01/23/2008 5:17 PM

Resistance and reactance for a cable are both proportional to length, so yes - the resistance per meter is 1/1000th of the resistance per km.

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#2

Re: cable resistance and impedance

01/23/2008 11:54 PM

The way you describe it, it makes no sense. First, describe the physical sizes, like how many wires, their material, sizes, distances from each other. What you want to use it for. Have not met a cable with 1 ohm/km. That is more like a busbar 1 meters on the edge, or some such. Reactance is frequency dependent. So start with a very good physical description and application. Then, maybe we see.

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#3
In reply to #2

Re: cable resistance and impedance

01/24/2008 12:39 AM

Actually, it does make sense, go to a electronics shop to buy some wire, the single cores (no matter how many strands or gauge) gives the wire R/km or R/M (R/meter)

For transmission line, say RG-58U Reactance, or some documentation has Impedance


http://www.benelec.com.au/pdf/coaxss.pdf

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#4

Re: cable resistance and impedance

01/24/2008 11:27 AM

In general, no you can't. Resistance is linear for good insulation and short distances (and longer distances for single wires - I think you have a multiconductor cable). But you quickly get into characteristic impedances and length dependence.

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