Abstract :
R. W. Atkinson (General Cable Corporation, Bayonne, N. J.): In his paper Mr. Shanklin contributes important data. However, some of his conclusions appear to be based not on these or other available data. In part, this discrepancy seems to be due to his placing perhaps an unwarranted weight on the “self-healing property.” He discusses this subject in a very interesting manner but he, himself, gives reason to discount much of its practical importance. For example, Mr. Shanklin states that at the higher pressures “this working-voltage stress is well below the ionization-voltage stress” and cites specifically cables designed for 80 and 40 pounds per square inch to confirm this point. Inasmuch as he also contends that it is ionization which produces this self-healing, it is difficult to see how he can expect any self-healing to occur in service at these pressures. He even indicates that what he says of higher pressures is true, though to a lesser degree, in cables intended to operate at a pressure as low as 12 pounds. He expects, however, that future reductions of insulation thickness will make operating stresses higher with respect to ionization stresses. This apparently may make the self-healing feature of some significance at very low gas pressure, but there is no reason to suppose that any such changes can bring stresses in high-gas-pressure cable to the point where the self-healing feature can be of any practical significance.
