Load Factor. The load factor of each underground line should be determined. It generally should not be less than 75% for typical transmission lines and should be 100% for dedicated generator leads. ADJACENT HEAT SOURCES Adjacent heat sources (i.e.: adjacent heat pipes, distribution lines, or transmission lines) are to be taken into account as outlined in Reference 3, p. 206 and pp. 227-229. Hot Spots should be identified throughout the cable system. BONDING SCHEMES Bonding schemes such as multipoint/single point/cross bonding etc. are to be taken into account for the rating of the cable. CABLE AND DUCT/PIPE CHARACTERISTICS The cable's characteristics (conductor size, type and stranding, insulation type and thickness, metallic shield type and thickness and/or size and number of wires, etc., jacket type and thickness) are to be taken into account. If the installation is in conduit or pipe, include the dimensions and type of conduit or pipe (if used), pipe or conduit filling medium (typically air, or dielectric fluid as in the case of high pressure dielectric fluid filled pipe type cable) as outlined in Reference 3, pp. 203-204. Installation Characteristics INSTALLATION CHARACTERISTICS The cross Section of the Cable Environment, depth of burial, spacing and configuration (vertical and/or horizontal spaced, close triangular etc) of adjacent phases, number of circuits, spacing and configuration of adjacent circuits and/or external heat sources, type of installation (direct burial or in conduit of pipe), type and dimensions of backfill material, type of native soil etc. as outlined in the EPRI Underground Transmission Systems Reference Book pp. 205-206 (1992 Edition).
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Sources: Procedures for Determining and Implementing Transmission Facility Ratings, Procedures for Determining and Implementing Transmission Facility Ratings