摘要
大型海上风电场一般离岸较远,主要依赖于高电容海底电缆将电能送出,可能产生较为严重的过电压。但海底电缆敷设于海底难以检修,所发生的故障一般为永久性故障,会给电力系统造成巨大损失。作为威胁海底电缆安全可靠运行的重要因素,海上风电场送出系统的工频过电压机理与特性亟待系统性的总结和研究。本文从原理上分析了海上风电场工频过电压产生的机理与特征;并基于ATP-EMPT对500 kV海上风电场及其送出系统进行建模,对海缆参数进行了修正,以保证模型的准确性;同时,仿真计算了在不同容量情况下,海上风电场及其送出系统的五种不同工况运行时,海缆的容升效应、单相接地故障、无故障突然甩负荷、单相接地故障突然甩负荷和两相接地故障甩负荷时的工频过电压,结合理论分析,最终总结了影响海上风电场送出系统工频过电压的因素及其影响趋势。
Large-scale offshore wind farms are generally far away from the shore, and mainly rely on high- capacitance submarine cables to send electrical energy, which may generate serious overvoltages. However, it is difficult to repair submarine cables when laid on the seabed. The faults that occur are generally permanent faults, which will cause huge losses to the power system. As an important factor that threatens the safe and reliable operation of submarine cables, the power frequency overvoltage mechanism and characteristics of the transmission system of offshore wind farms urgently need to be systematically summarized and studied. This paper analyzes the mechanism and characteristics of power frequency overvoltage in offshore wind farms in principle;then, based on ATP-EMPT, the 500 kV offshore wind farm and its delivery system are modeled, and the submarine cable parameters are corrected to ensure the accuracy of the model;what’s more, the simulation calculated the power frequency overvoltage of five various fault conditions (the capacity rise effect of submarine cables, single-phase grounding faults, no-fault sudden load rejection, single-phase ground fault sudden load rejection, and two-phase ground fault load rejection) when the transmission system are operating in five different working conditions under different capacity conditions. Combined with theoretical analysis, the factors that affect the power frequency overvoltage of the offshore wind farm transmission system and their influence trends are finally summarized.
