美丽山二期直流线路突变量保护优化研究

Optimization of line derivative protection in Belo Monte phase two ultra high voltage DC project

特高压直流输电双极长线路间存在非常明显的互感影响,当一极线路故障时,另一极线路电压因受互感影响会以较快的速度降到较低值,此现象与直流线路发生接地故障时的电压变化规律基本相同,容易引起直流线路电压突变量保护误动。本文首先对直流线路突变量保护误动的机理进行深入分析,利用双极线路互感影响造成的电压下降与实际接地故障造成的电压下降在恢复特性上的差异性,提出考虑互感影响时的闭锁电压突变量保护策略,并在实时数字仿真试验平台上对该策略进行试验验证,证明了所提策略的有效性,为其他直流工程提供参考。

There is a very obvious mutual inductance between UHVDC bipolar long lines.When one pole line fails,the voltage of the other pole line will drop to a lower value at a faster speed due to mutual inductance.This phenomenon is basically the same as the voltage variation law of DC line when grounding fault occurs,which is easy to cause misoperation of DC line derivative protection.Firstly,this paper deeply analyzes the misoperation mechanism of DC line derivative protection.Taking advantage of the difference in recovery characteristics between the voltage drop caused by mutual inductance of bipolar line and the voltage drop caused by actual grounding fault,a blocking voltage derivative protection strategy considering the influence of mutual inductance is proposed,and the strategy is tested and verified on the real-time digital simulation test platform.The effectiveness of the proposed strategy is proved,which provides a reference for other DC projects.