Protective covering for lead-sheath power gables

THE MAJORITY of failures of impregnated-paper or varnished-cambric lead-covered power cable are due to the entrance of moisture through a break of some kind in the lead sheath. The sheath failures may be due to corrosion, electrolysis, mechanical damage, fatigue attributable to either vibration or cable movement, or high internal pressure. Corrosive action or electrolysis in some degree are fairly common to all lead-covered cables installed in ducts while damage due to mechanical failure is generally confined to those cables which are subjected to large daily variations in load. This latter type of failure has become of increasing importance with the higher loads which have been imposed on power cables during recent years.