A-C Resistance of Segmental Cables in Steel Pipe

In recent years, there has been a very great increase in the use of pipe-type systems for long, high-voltage impregnated-paper transmission feeders. Thus, a detailed knowledge of the factors influencing the a-c losses of large size conductors with relatively low skin-proximity effect characteristics is of value to all cable and operating engineers. This paper reports the results of a study of the effective a-c resistance of a compact type of segmental conductor in sizes from 1,000,000 to 2,000,000 circular mils, in air and in steel pipe, with equilateral triangular and cradle configurations. From analysis of the data, an approximate separation is made of losses occurring in the conductor, the outer shield structure and the steel pipe. These component losses are compared with accepted and derived formulas, and application of the data is thus broadened by use of mathematical methods. Based upon the suggested methods of computation, tables are given of losses of cables in steel pipe over a range of conductor sizes and voltage ratings.