Experimental validation of ultra-shortened 3D finite element models for frequency-domain analyses of three-core armored cables

TL;DR

This work validates an ultra-shortened 3D-FEM model (SUSM) for frequency-domain analyses of three-core armored cables (TCACs) by comparing against experimental data from three real cables. The SUSM achieves substantial reductions in computation time while preserving accuracy for key metrics, including total losses, positive/zero sequence impedances, induced sheath currents, harmonic resonances, and magnetic-field distributions. A two-step SUSM procedure enables accurate harmonic impedance predictions, with resonant frequencies matching measurements to within about 1%, and zero-sequence predictions remaining robust except at very low frequencies. A time-domain example demonstrates the SUSM’s applicability to EM transient analyses, showing close agreement with EMTP-RV results and highlighting SUSM as a practical, complementary tool for TCAC design and evaluation in offshore wind applications.

Abstract

Recently, large offshore wind power plants have been installed far from the shore, using long HVAC three-core armored cables to export power. Its high capacitance may contribute to the appearance of unwanted phenomena, such as overvoltages or resonances at low frequencies. To adequately assess these problems, detailed and reliable cable models are required to develop time-domain/frequency-domain analyses on this type of cables. This paper presents, for the first time in the literature, an assessment on the performance of 3D finite element method-based (3D-FEM) models for developing frequency-domain analyses on three-core armored cables, confronting simulation results with experimental measurements found in the literature for three real cables. To this aim, a simplified ultra-shortened 3D-FEM model is proposed to reduce the simulation time during frequency sweeps, through which relevant aspects never analyzed before with frequency-domain 3D-FEM simulations are addressed, such as total losses, induced sheath current, magnetic field around the power cable, positive and zero sequence harmonic impedances, as well as resonant frequencies. Also, a time-domain example derived from the frequency-domain analysis is provided. Remarkable results are obtained when comparing computed values and measurements, presenting the simplified ultra-shortened 3DFEM model as a valuable tool for the frequency-domain analysis of these cables.

Figures (13)

• Figure 1: USM: Rotated periodicity and current density distribution in TCACs.
• Figure 2: USM: Electric field distribution (V/m) within TCAC's fillers.
• Figure 3: Mesh employed for the armor wires when using the USM or the impedance boundary condition in the SUSM.
• Figure 4: Cable C2 (SB): positive and zero sequence series resistance and inductance as a function of frequency (derived by the SUSM).
• Figure 5: (a) Relative permeability for a LG steel (three cables), and (b) dielectric loss factor as a function of frequency (C2 cable).