Technical Report Bahder, G ; Katz, C ; Seman, G W

with the cables in pipe were developed, and the permeability properties of the steel pipes were experimentally determined. Results of the tests performed indicate that similar cables with copper conductors with bare, tin-coated strands exhibit similar ac/dc resistance ratios. Cables with enamel coated copper and aluminum strands have lower ac/dc resistance ratios than the above cables. Tests performed at room temperature, after exposing the conductor to elevated temperatures, indicate that in some cases the room temperature ac/dc resistance ratios are affected by the maximum temperature to which the conductor was exposed. Comparison of measured values with calculated values (using the Neher-McGrath method) confirms that this method can also be used for aluminum conductors at room temperature and for copper and aluminum conductors at operating temperature. The accuracy of the Neher-McGrath method has been improved by the use of a new transverse conductance facter k/sub pc/ and a new in-pipe factor. The method developed provided only a limited agreement between calculated and measured values. The attainable accuracy is circumscribed by the nature of the boundary conditions, and by the limitation on the detail which can be modelled.

Results are presented of investigations on the determination of ac/dc resistance ratios of high and extra high voltage pipe-type cables with large cross-section segmental conductors. The measurements included 115, 345 and 765 kV cables with copper and aluminum conductors. Conducting and insulating coatings were used on the copper strands. Aluminum strands were covered with their natural oxide coating. Measurements were made in-air and in-pipe in close triangular and cradle configuration. Measurements with cables in-pipe were initially performed at temperatures up to 150/sup 0/C and later only up to 115/sup 0/C. Improved analytical formulations for the calculation of the power losses more »