The AC Resistance of Segmental Conductors as Used in Power Cables

Multiconductor cell analysis of skin effect in Milliken type cables

“…Since these blocks are characterized by the corresponding admittance matrices (suitably partitioned) Y and G , it is possible to apply the "cascade procedure" presented in Appendix A (see Figs. 7 and A.1), so to obtain the matrix Y 1 , which characterized the "elementary cell" (where the core conductor with stranded insulated wires is composed of 63 regular bundles) on the small length 1• = 1( /6) = one-sixth of the lay length of layer 4; (in the following case studies = 24 cm has been assumed accordingly to Discussion in [8]).…”

“…In this paper the MCA has been suitably adapted for investigating the skin effect in Milliken type (M-type) cables. As well known, the ampacity of cables with great cross-sectional area can be seriously reduced, at power frequency, by the skin and proximity effects: numerous contributions [5][6][7][8][9][10][11][12][13][14][15][16][17], appeared in the technical literature after that of Lord Kelvin (1873), have allowed studying in depth the experimental and theoretical features of this problem. On this topic, a Cigré WG has delivered a technical brochure [5] about large cross-sections, advertising that [6] "there is no agreed method to define the value of the a.c. resistance to take into account when calculating the ampacity of such cables, whereas it is a critical parameter".…”

Optimized conductors for XLPE cables with a large cross-section

“…Calorimetric methods are time consuming. Second, there are the electric resistance measurement methods [2,[16][17][18][19][20]. These methods are based on the measurement of the conductor current and the determination of the voltage contribution in phase with this current.…”

“…The loop current is determined by the induced voltage U ind and by the loop impedance. Conductors with unidirectional layers have a lower induced voltage than conductors with contra-directional layers [2]. Therefore the AC losses can be reduced by using unidirectional layers for uninsulated strands.…”

“…On the other hand, the conductor strands of XLPE (cross-linked polyethylene) cables are not oil impregnated which is reported to significantly enhance the AC resistance [2]. The compression forces on the conductor are higher for XLPE cables due to the high shrinking stress of the extruded insulation.…”