Cable insulation resistance constant (K) calculation

[alwaink]

Hi,

For cable insulation resistance calculation, the equation goes:

IR = K * log (D/d) [megaOhm-1000ft]

where D = diameter of insulated conductor
and d = diameter of copper inductor

ICEA has some K numbers for PVC and rubber. But how is K calculated? It's nowhere explained. I've come across this equation for K, but the source is not cited:

K = (p*2.3026E-6)/(2*pi*12,000*2.54) where p = volume resistivity [ohm-cm]

The denominator (2*pi*12000*2.54) is simply conversion to 1000ft. But I'm not sure what 2.3026E-6 is. Has anybody seen this equation from any standard so that I can cite the source in my document please? Or would this be like a common-sense V=IR equation that I'm not aware of?

Thanks

 

[electricpete]

The electric field is proportional to 1/r. When you integrate it you get a natural log (ln).

Your log is base 10. Conversion is 1/log10(e)=2.302

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