Copper connotations

Heretofore, joining large aluminum underground power cable to aluminum or copper power cable with compression connectors was not feasible because of premature failure of the connector joint under electrical current loading. Unlike the long andbulky compression connectors used on bare overhead power lines where space is not a premium, underground compression connectors must be short to keep manhole size small and to reduce the time required to insulate the joint with hand-wrapped tape or otherinsulating materials. Overhead line connectors receieve appreciable cooling from air currents whereas commonly used paper or plastic insulation restricts the cooling of underground cable joints. Metal particle-filled grease joint compounds used inoverhead line compression connectors are not used for underground cable for several reasons. First, its use is precluded because of the possiblity of migration of the compound into the paper or along the insulation resulting in voltage puncture of theinsulation from ionization. Secondly, joint compounds of grease do not offer much improvement over no compound because grease will move under pressure and therefore does not constrain relative movement of connector and conductor strands whereashardenable resins such as epoxy do.