The Effect of Internal Vacua Upon the Operation of High-Voltage Cables

It has been known for some time that the internal mechanical pressure of cables is a factor in the quality of the insulation, and that the oil used in impregnating paper for cable insulation has a high thermal expansion which may alter the internal pressure of cables with varying temperature. This paper considers the rate of pressure equalization in cables and the relative effects of slow equalization upon long and short cables, indicating that there may be considerable difference in dielectric properties depending on the length and past history in regard to temperature cycles. Means of overcoming these differences are suggested. The paper is suggestive rather than demonstrative and it is proposed to publish a sequel giving experimental proofs of the facts stated.