Numerical Simulation of Three-Dimensional Electric Field in a Prototype of 35kV Offshore Single-Point Mooring Device

The single-point mooring (SPM) system is a critical part of the FPSO device, which can realize the transfer of electrical energy (via the high voltage conductors), communication and control information (via optic fiber) and oil/gas fluids (via tube system) in the marine environment. To enhance the transmission ability of electric power, a relatively higher voltage (e.g., 10-35 kV) can be employed, which however requires detailed analysis on electric field distribution. In this study, numerical simulation of electric field distribution on a prototype of 35 kV SPM device was involved. Finite element method (short-time) was used to calculate the electric field, which is realized by COMSOL. The results show that the through-wall bushing of the busbar is the place of maximum electric field, which is due to the relatively small insulation distance and the existence of some tip points. The triple junctions of separate insulators are another region of electric field intensification, due to the dielectric mismatch between metal, insulator and air. The slip ring system, which is initially believed to be the weak point of SPM system, do not have very high electric field due to the existence of shielding structures. This study clarifies the electric field distribution of the $35 \mathbf{k V}$ SPM system, and the future works will be related to the geometrical optimization in the high voltage insulation system of the 35 kV SPM.