Discussion Group C37D on Submarine Cables will have several presentations at the spring meeting. These include:

“Inter array cable size optimization case study / CAPEX vs Total Ownership Cost” by George Georgallis, Hellenic Cables

Abstract: “In recent years Offshore Wind Farms have grown rapidly in power- some exceeding 1 GW-  and wind turbine number per farm – 40 to 80+ –  and their numerous configuration possibilities have motivated the use of optimization techniques. This presentation considers a case study using such an optimization formulation to find the techno-economic optimum for the cable sizing in string feeders. This is succeeded by minimizing the sum of capital and operational costs, with the latter being calculated by more accurate loss estimation formulae compared to the relevant IEC standard. In the base reference case, the cables are initially dimensioned to optimize CAPEX by just fulfilling the ampacity requirement. It is concluded that a more cost-effective solution by the end of service life can be achieved by the proposed method. “

Title To Be Determined, by Dr. G.J. Anders

Abstract: When a 3-core submarine cable enters the land portion of the route, the armor is stripped and grounded. From that point until a transition joint, the three separate single core cables are laid in the ground, usually in a flat formation. The distance between the armor grounding point and the transition joints is usually short, up to 5 m. In the standard cable design procedure, it is assumed that the great length of the submarine cable limits the sheath circulating currents throughout the entire run of the circuit. However, since the single-core cable in the land section have increased spacing between the phases, the currents which are generated in this part of the route are much larger than in the section of the submarine cable far away from the shore. Combination of the 3-core submarine cable with semiconducting jackets around the cores and the three single core cables in the land portion results in a substantial increase of the circulating sheath currents in the submarine cable as well. These currents and their effect on the cable temperature will be presented on an example of a 220 kV 3-core export cable..

Since this effect results in a significant temperature increase, general recommendations for a reduction of the end effects in submarine installations will also be discussed.