Underground conduit for electric power systems

ELECTRIC CONDUITS of one type or another have been in use since the beginning of the electric power industry. Construction practices and materials are fairly well standardized within companies. There is no accepted single standard for the industry, and it is probable that no single standard could be designed that would be satisfactory. However, since the fundamentals and basic design considerations are the same throughout the industry, any discussion concerning these principles is pertinent to all conduit design. In recent years, probably the only new development involving conduit construction is the installation of high-voltage transmission cable in steel pipe with gas or oil under high pressure. The cost and lack of flexibility usually restrict this new system to high-capacity transmission uses.