MOISTURE PERMEATION AND ITS EFFECT ON COMMUNICATION CABLE
BELL TELEPHONE LABS INC MURRAY HILL NJ
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The paper covers certain aspects of the problem of water in buried telephone cables. In the first part of the paper the permeation of water vapor through plastic sheath is discussed and the concept of the permeation time constant is introduced. A permeation pumping mechanism which can accumulate significant amounts of liquid water in buried cables is described. This mechanism depends on air flow rate and temperature changes in pressurized cables. In the second part of the paper the effects of small amounts of water on the capacitance and conductance of polyethylene insulated cable at voice and carrier frequencies are reported. In addition, some estimates are given of the likelihood of conductor cutoff by electrochemical corrosion in wet PIC cable. Finally, the problem of the junction of pressurized PIC and pulp cables is considered and the effect of humid air from the PIC cable on the electrical properties of the pulp cable are reported.
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