Grounding System Analysis of 220 kV Power Cable Lines Installed Underneath a Bridge

Abstract

Power cables installed underneath the bridge have become vital in the cross-sea power transmission system <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.</i> The design of grounding system is a decisive factor which determines the safety and reliability of these cables. In this paper, the nodal admittance matrix of the cable system is established considering the influence of the overhead laying condition and the coupled line model is used to improve the calculation efficiency. A matrix solution method, which can greatly reduce the dimension of the nodal equation, is proposed for the steady-state analysis of the grounding system. The grounding system designed for 220 kV cable project of Zhoudai Bridge in Zhejiang Province of China is also investigated. The results show that, compared with the induced voltage, the circulating current is the main factor affecting the ampacity of the cable system. Connecting the impedance at the cable joint can effectively reduce the power loss caused by circulating currents. A guideline for the grounding system design of the power cable lines installed underneath a bridge is proposed in this paper.