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BELL SYSTEM TECHNICAL JOURNAL 



of these hydrocarbon chains. This may explain why silk has a higher 

 resistance than cotton for a given moisture content. It might be 

 expected that silk, due to these hydrocarbon barriers in the current 

 path might also have a higher dielectric breakdown under potential 

 stress. 



0.05 0.10 0.15 0.20 0.25 0.30 0.35; 



MOISTURE CONTENT IN PER CENT OF TOTAL VOLUME 



Fig. 9 — Relation between power factor components of cable paper 

 and moisture content. 



Whitehead, ^^ in a study of the effects of moisture on power cable 

 paper insulation, obtained data on the change of power factor with 

 increasing moisture content. Figure 9 shows this relation. It will 

 be noted that the conduction component (tan ypi) of the power factor 

 rises sharply as the moisture content of the paper exceeds 0.2 per cent 



