Identifier: cyclopediaofappl05amer (find matches)
Title: Cyclopedia of applied electricity : a general reference work on direct-current generators and motors, storage batteries, electrochemistry, welding, electric wiring, meters, electric lighting, electric railways, power stations, switchboards, power transmission, alternating-current machinery, telegraphy, etc.
Year: 1916 (1910s)
Authors: American Technical Society
Subjects: Electric engineering
Publisher: Chicago : American Technical Society
Contributing Library: Northeastern University, Snell Library
Digitizing Sponsor: Northeastern University, Snell Library

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Ducts safe for workmen to enter the splicing vault until the impure air hasbeen pumped out. Auxiliary ducts are laid over the main ducts and distributionis accomphshed from handholes. It is customary to ground the lead sheaths of the cables atfrequent intervals, thus in no way depending on the ducts, evenwhen made of insulating material, for insulation. Cables. Well-insulated copper cables are used for under-ground systems. On account of the fact that various materials,such as acids and oils which are injurious to the insulation, comein contact with the cable, it is necessary that it be protected insome manner. A lead sheath is employed for this purpose. Thissheath is made continuous for the whole length of the conductor,and with its use it is possible to employ insulating materials suchas paper which, on account of being readily saturated by moisture,could not be used at all without such a hermetically sealed sheath.Lead containing a small percentage of tin is usually employed for 90
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SPECIAL 135-FOOT TOWERS USED FOR MISSISSIPPI RIVER CROSSING AT HAMILTON, ILLINOIS, IN CONNECTION WITH THE MISSISSIPPI POWER DAM AT KEOKUK, IOWA Courtesy of Mississippi River Power Company POWER TRANSMISSION 81 LEAD -//VSUl AT/ON this purpose. The sheath may consist of a lead pipe into whichthe cable is drawn, after which the whole is drawn through suitabledies, bringing the lead in close contact with the insulation, or thecasing may be formed by means of a hydraulic press. Yarns thoroughly dried and then saturated with such materialsas paraffin, asphaltum, rosin, etc., paper, both dry and saturated,rubber, and varnished cambric Are the materials generally employedfor insulation. When paper is employed, it is wound on in strips,the cable being passed through a die after each layer is applied, afterwhich it is dried at a tem-perature of 200° F. in orderto expel moisture. Afterbeing immersed in a bathof the saturating compoundit is taken to the hydraulicpresses where the leadsheath is p

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