Summary
The use of HVAC three-core submarine cables has increased with the build-out with offshore wind farms over the last two decades, which employ them both for the connection to mainland and the interconnection of the wind turbines. The sequence impedance of the cables is a key component in the power system design and stability studies. However, the complex geometry of the submarine cables, with the helical core bundle and armour, results in a three-dimensional electromagnetic field that not all the available calculation methodologies can address accurately. The widely recognised CIGRE TB 531 on cable systems electrical characteristics provides an analytical method for the impedance calculation of 3-core submarine cables. However, that method has a number of shortcomings which compromises the accuracy of the results, among others the omission of the cable armour layer as a parallel return path for the zero sequence impedance (Z0), the lack of guidance to include the skin and proximity effects in the impedance of the conductor, the exclusion of the eddy currents in the screens, and the insufficient applicability of the formulae for the high frequencies often required in stability studies.
Read more Read lessThis paper aims to provide guidance on the calculation of sequence impedances for HVAC 3core armoured submarine cables by comparing the results of selected upgraded analytical and numerical calculation methodologies recently published: the three‑dimensional finite element
“ultra‑short periodic” model; the analytical method presented in the CIGRE paper B1‑10693; the CIGRE Technical Brochure 908 for positive‑sequence impedance; and the Carbon Trust
Offshore Wind Accelerator “Sequence Impedance of Submarine Cables” (OWA SISC) methodology for zero‑sequence impedance. The study presented in this paper covers the calculation of positive and zero sequence impedances at power and high frequencies for typical three-core submarine cables used in offshore wind farms, including an export cable with separate lead sheath and an array cable with screen wires and laminated foil.
The study presented in this paper concluded that the analytical methods from the CIGRE
TB 908 and the OWA SISC method produce impedance results comparable to the finite element analysis for the impedance calculation of the typical export and array cable designs. This has the major technical benefit of retaining more readily standardisable analytical forms which can be solved with high computational efficiency, while still producing reliable results comparable to the more complex and less standardisable FEA numerical modelling. This is particularly valuable for the high-volume calculations required during wind farm project development and early execution stages.
Additional informations
| Publication type | Session Materials |
|---|---|
| Reference | B1_11712_2026 |
| Publication year | |
| Publisher | CIGRE |
| Country | Denmark |
| Study committees | |
| File size | 975 KB |
| Price for non member | 30 € |
| Price for member | 30 € |
Authors
GAROLERA Anna - Ørsted Wind Power; KVARTS Thomas - Ørsted Wind Power; HUANG Ziyi - Ørsted Wind Power; CALLENDER George - University of Southampton; GODDARD Kevin - University of Southampton; PENG Jinsheng - Ørsted Wind Power; COJOCARU Claudia - Ørsted Wind Power; RZEMPOLUCH Joanna - University of Southampton; CHAUDHARY Sunny - University of Southampton
Keywords
HVAC, Submarine Cable, Sequence Impedance, Analytical Calculation, Finite Element Analysis
