Economical loading of underground cables

Load ratings for underground electric power transmission cables for 2 typical metropolitan load cycles are computed in this paper by the method of harmonic analysis of load cycles. Test data are given which agree reasonably well with theoretical calculations. A logical basis for emergency rating of cables also is demonstrated. A comparison of costs of transmission for various duct conditions indicates that large conduit systems are not economical because of the lower ratings necessitated by the greater heat dissipated.