MEASUREMENTS IN MULTIPAIRED CABLES 



659 



the cable did not fill completely, because small bubbles of either air or 

 ethylene gas formed during the injection process and would not "wash out" 

 by continued flow. While these results are short of the objective, they are 

 close enough to be useful. 



22 

 21 

 20 

 19 

 18 

 17 

 16 

 15 



0.18 0.20 0.22 0.24 0.26 0.28 0.30 



d/2S 



Fig. 3 — e/Cmut as a function of d/2S, SD. 



0.32 



0.34 



The remaining air in the cable, occupying interstitial space, should not 

 reduce the dielectric constant below that of polyethylene (2.26) in propor- 

 tion to the percentage of air volume. This is because the electric field is 

 weaker in the interstitial space than in the space immediately surrounding 

 the conductors. The dielectric constant of the experimental cable should, 

 therefore, be somewhere between 2.26 and 1 + (93% of 1.26) = 2.17. 



