Computing the Wide-Band Earth Return Impedance of Submarine Cable Considering Complex Paths

Abstract

Because of the various earth return pathways in practical projects, calculating the wide-band earth return impedance of submarine cable is problematic. Using the dynamic Hertz magnetic potential, the formula for estimating the earth return impedance has been obtained based on the three-layer structure of air, sea water, and seafloor. Furthermore, in the frequency range of 50 [Formula: see text] 10 MHz, the enhanced complex image approach and numerical integration method have been developed to compute the earth return impedance. The suggested iterative complex image method outperforms the classic complex image method in terms of accuracy and computation speed, with a global fitting error of less than 10−6. Finally, the impact of various models on the real and imaginary parts of submarine cable wide-band earth return impedance has been investigated. The results demonstrate that the actual component has a more complicated variation, whereas the imaginary part is clearly affected by the skin effect, with a bigger difference in the high-frequency range. The method presented in this research can be utilized as a supplement to existing methods, as well as a reference methodology for analyzing the influence of over-voltage on submarine cable engineering.