Performance of different grounding systems of 500 kV XLPE long submarine cables based on improved multiconductor analysis method

•The accurate distributed impedance matrices of the single-core submarine cable system are established to calculate the electrical parameters considering the effects of the multilayer soil laying condition and semiconducting sheath.•The improved multiconductor analysis method based on the coupled line model and matrix cascading algorithm is proposed to further improve the calculation efficiency.•The characteristics of the three main grounding methods for the single-core submarine cables are fully revealed and analysed. The grounding system is a decisive factor in the safety and reliability of submarine cables used for marine transmission systems. In this paper, the accurate matrices of distributed impedance of the submarine cable system are established considering the effect of the multilayer soil laying condition. The improved multiconductor analysis method, which has good calculation efficiency and accuracy, is proposed to analyse the cable grounding system under the steady-state power-frequency operating conditions. The performance of different grounding methods of the Zhoushan 500 kV XLPE submarine cable project in Zhejiang Province of China is investigated. The results show that the grounding methods of solid-bonding with intermediate grounding points and solid-bonding with semiconducting sheath are more promising than the conventional solid-bonding grounding method for the long submarine cable system due to the reduction in the induced voltage of metallic sheath as well as lower power loss. A guideline for the grounding system design of the long submarine cable lines is proposed in this paper.