The calculation of the outside thermal resistance of a buried cable system related to uniform, nonuniform and temperature-dependent resistivity of soil can be made, if a suitable transformation of the thermal field is automatically drawn and the resistance is computed on the transformed field. A suitable conformal transformation is analysed-giving rise to maps of the transformed field. On the maps, the calculation of resistances involves simple operations even when the soil is nonuniform and of temperature-dependent resistivity, provided some approximations are introduced. The errors incurred by such approximations are slight and can be checked, when necessary, by direct computation of the thermal field. The calculation of resistances on the maps can also be carried out by means of automatic design programs.
LIST OF SYMBOLSc = cable circumference D = cable diameter g = thermal resistivity hj = constant proportional to power loss of source i = general numerical suffix kj, l n j = lengths read on transformed maps m ' = number of source pairs p = vertical distance of cable centre from x axis q = horizontal distance of cable centre from y axis R = thermal resistance r = modulus of co-ordinate z Ru R 3 = thermal resistance for lateral cables R 2 = thermal resistance for centre cable 5 = position of cable centre (q -jp) T = temperature T c = isotherm at which soil resistivity changes (normally 50°C) T Q = ambient temperature Ti = cable surface temperature W = cable power loss Y o = earth surface in transformed plane Yj_ = cable surface in transformed plane z = complex co-ordinate (x + jy) in original plane Z = complex co-ordinate (X + jY) in transformed plane zj, zi = co-ordinates of point sources in original plane 6 = displacement of point source 6 = argument of co-ordinate z
The report describes the philosophy which is being followed in approaching the problem of the transmission of bulk electric power at very high voltages by means of long distance submarine cables laid in exceptionally deep waters up to 5000/6000 ft.After a careful survey of the present state of the art for all possible candidatc ables, it is planned to focus attention on the most promising ones with reference to some representative sites of future OTEC plants. It is intended that the chosen cables will undergo full technical design, economic evaluation and reliability analysis. If candidate cables, according to the state of the art, are not sufficiently developed for one or more representative sites, then suitable research and development work will~be proposed.Attention is also paid to cable accessories and laying operations, with special emphasis on the importance of reducing the number of joints, on the exceptional performance required for the laying equipment and on the embedment problem.After covering the main problems of the bottom c~bles connecting the substations on the shore end to the proximity of the OTEC power plants, some hints are provided on the interface with the riser cables connecting the standing bottom cables to the floating power plants.
This paper was prepared for presentation at the Sevent~A~nual OffshO~~Techn~logy Conference to be held in Houston, Tex., May 5-8, 1975. PermlSSlon to co~y 1_ restrlcted to an abstract of not more than 300 words. Illustrations may not be copled. Such us~of an abstract should contain conspicuous acknowledgment of where and by whom the paper 1S presented.
ABSTRACTThe paper reviews design, manufacture and laying of submarine power cables, according to the~xperience of one of the largest manufacturers in the world.
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