海上风电柔性直流送出海缆过电压研究

Study on Overvoltage of Submarine Cable Applied in Offshore Wind Power VSC-HVDC Transmission

海上风电柔性直流送出是目前远海风电常用的输送方式,在整个风电输送系统中,直流海底电缆作为柔性直流换流站的连接单元,其安全性和运行可靠性对于整个系统起着至关重要的作用。以规划中的某海上风电柔性直流送出工程的直流海底电缆为研究对象,在PSCAD/EMTDC中建立整个海上风电柔性直流送出系统的仿真模型,考虑了联接变网侧、联接变阀侧、桥臂电抗器阀侧和直流侧共17种故障类型,通过仿真计算得出直流电压为±250 kV的海底电缆芯线对地的过电压最大值为506.4 kV和对应的故障工况为直流海缆起点接地故障。考虑30%的绝缘裕度,确定额定直流电压为±250 kV的直流海缆绝缘水平为660 kV。计算结果可为提高海缆运行安全性提供重要参考。

At present,VSC-HVDC transmission is a common choice for offshore wind power grid connection.In the whole wind power transmission system,DC submarine cable,as the connection unit of VSC-HVDC converter stations,plays a crucial role in the safety and operation reliability of the whole system.Based on the DC submarine cable in a planning offshore wind power VSC-HVDC transmission project,a simulation model of the whole offshore wind power VSC-HVDC system is established in PSCAD/EMTDC.A total of 17 kinds of fault types may happen in the system are considered.The fault zones include coupling transformer grid side,coupling transformer valve side,bridge arm reactor valve side and DC side.As a conclusion,the highest core-ground overvoltage of±250 kV submarine cable is 506.4 kV and the corresponding fault type is the grounding fault at the start point of DC submarine cable.Considering 30%insulation margin,the insulation level of the DC submarine cable with rated voltage of±250 kV is determined to be 660 kV.The calculated results can be an important reference for improving the safety of submarine cable operation.