Hybrid Method to Compute the Total Series Impedance of Submarine Power Cables

Abstract

Subsea umbilical cables are complex systems that are typically hard to electrically model. The identification of electrical parameters of subsea umbilical are fundamental in the analysis of the behavior of such cables when introduced into a system-level model. This work presents an approach for calculating the series impedance matrices of a submarine cable using a hybrid method including finite element analysis and analytical equations. Commercial electromagnetic transient programs do not take into account the proximity effect, and only coaxial cable systems are supported, excluding more complex cable systems, like those used for off-shore oil exploration. The application of the Finite Element Method (FEM) for internal cable parameter determination overcomes these problems. Otherwise, using analytical expressions to calculate external impedance simplifies the FEM implementation, reduces the computation efforts and allows to calculate the external impedance with fullwave models, overcoming the limitations of low-frequency finite elements software. The results are validated against EMTP-RV, which is a professional software for power system transients. More significant differences are observed with the increase in frequency due to effects not considered by the commercial software, which are covered in the finite element simulation.