282 



BELL SYSTEM TECHNICAL JOURNAL 



equally well to the curves in Fig. 3, which have been used to evaluate the 

 liability of such cable to lightning damage. 



100 

 95 

 90 



75 



70 



2 60 



55 



45 



•J 40 



35 



30 



25 



20 



0.3 0.4 0.6 0.8 1.0 1.5 2 3 4 



NUMBER OF CURRENTS EXCEEDING ORDINATE 



5 6 7 8 9 10 



Fig. 2 — Incidence of currents exceeding ordinate per 100 miles and 10 thunderstorm 

 days. 



1 .2 Propagation of Currents A long Cable 



The current entering the cable at or near the stroke point, depending on 

 whether a direct stroke or a nearby stroke to ground is involved, is at- 

 tenuated as it travels along the sheath towards remote points. The cur- 

 rent leaving the sheath must flow through the adjacent soil, and the leak- 



