308 



BELL SYSTEM TECHNICAL JOURNAL 



Leakage Conductance 



The variation in the dielectric constant of the insulating layers of paper 

 is further reflected in the leakage conductance, G. This is probably the 

 most inconstant of the parameters and is a function of separation of the wires 

 and their diameters, as well as frequency and temperature and the nature 

 of the dielectric. Humidity, if present, is a highly important contributor 

 to high leakance, but in properly dried cables the humidity is not very great. 

 It will be seen in the later discussion of attenuation and the factors affecting 

 it that conductance is a much less important factor, relatively, than it is for 

 open-wire lines. 



d 400 



5 



300 



200 



20 



30 40 50 60 

 FREQUENCY- KILOCYCLES 



80 



90 



Fig. 10 — Conductance per mile vs. frequency — 19 gauge pairs 



The curves of Fig. 10 show the variation of conductance of 19-gauge pairs 

 with frequency at five temperatures from zero to 120° F. When plotted on 

 log-log paper these curves are nearly linear, showing that conductance varies 

 with frequency approximately according to a formula of the type 



G= cF* 



(7) 



where a is about .0001 X 10" and k is about 1.33 for the 57° data. F. B- 

 Livingston in a paper on conductance in cables stated that for the data 

 there given k averaged about 1.3. 



The range of conductance from pair to pair in a reel is about ±11 per 

 cent from the average and the standard deviation about 5.5 per cent. 



" F. B. Livingston, "Conductance in Telephone Cables," Bell Laboratories Record, 

 Vol. XVI (Dec. 1937) p. 141. 



