Condenser cone for H.T. cable ends and joints

A h.t. cable is usually prepared for voltage and power-factor testing by stripping the lead and metallised paper away from the ends. When voltage is applied to the cable and raised in value, stress concentration occurs at the termination of the lead sheath, perhaps ultimately resulting in a flashover. The author discusses means for counteracting this concentration by making the voltage gradient more uniform along the length of exposed dielectric. He then describes a special device called the condenser cone for effecting this purpose. It consists of a number of concentric cylinders the outer being connected to the cable core and the inner one to the sheath. When voltage is applied to the core and the sheath earthed, the potential of each cylinder is governed by the values of the interlinked capacities, and these may be adjusted to give an equal increment of voltage across each pair, resulting in a uniform gradient along the dielectric. The article is well illustrated by diagrams and drawings, and a table giving the dimensions of standard cones as used by the author is added. The application of the device to joints as well as to cable ends is described.