基于非解耦节点导纳矩阵的随桥电缆接地方式研究

Study on Bridge-Cable Grounding System Based on the Non-decoupling Nodal Admittance Matrix

由于桥梁结构的特殊性,随桥电缆的接地方式成为决定跨海输电系统安全可靠的重要因素。该文考虑架空敷设环境的影响,推导了随桥电缆系统的单位长度串联阻抗矩阵和并联导纳矩阵;引入矩阵的非解耦形式,对节点导纳矩阵的计算进行简化;推导同阶和不同阶节点导纳矩阵的级联公式,构建随桥电缆系统稳态计算的矩阵解法。利用该矩阵解法对舟岱大桥220kV随桥电缆工程开展了接地方式研究。研究结果表明:金属护套和回流电缆的感应电压幅值最高可以达到87.15V;金属护套和回流电缆的环流幅值最高可以达到79.57A。环流造成的总损耗功率达到360.34kW。在电缆交叉互联接头处串联阻抗可以有效减小损耗,阻抗相角为60°时降损效果最优。所做工作为随桥电缆系统的接地方式研究提供了新的计算方法和工程应用参考。

Due to the particularity of the bridge structure,the grounding method of the bridgecable has become an important factor that determines the safety and reliability of the cross-sea transmission system.In this paper,considering the influence of the overhead installation environment,series impedance matrices and shunt admittance matrices of the bridge-cable system are derived;the non-decoupling form of the matrix is introduced to simplify the calculation of the nodal admittance matrix;the cascade formula of the same order and different order nodal admittance matrix are deduced,a matrix solution method for the steady-state calculation of the bridge-cable system is constructed.For the 220kV bridge-cable project of Zhoudai Bridge,the grounding method is studied.The results show that the maximum induced voltage amplitude of the cable sheath and earth continuity cable can reach 87.15V.The maximum circulating current amplitude of the cable sheath and earth continuity cable can reach 79.57A.The total power loss caused by the circulating current reaches 360.34kW.Connecting the impedance at the cross-bonding joint can effectively reduce the loss,and the loss reduction effect is the best when the impedance phase angle is 60°.The work done provides a new calculation method and engineering application reference for the research on the grounding method of the bridge-cable system.