高压直流输电系统在全球能源互联网战略中占有重要地位，对于直流系统输电线路研究表明：继电保护快速、可靠动作对维持直流系统的稳定至关重要。因此，对高压直流输电线路的故障识别及继电保护进行研究具有重要意义。通常情况下，高压直流输电线路的主保护为行波保护，后备保护为低电压保护和纵差保护等，然而由于保护原理的不同、原则设置的不统一、特殊情况下（如高阻接地故障）无法准确定位故障等一系列问题一直困扰着众多学者，因此，研究一种新的保护策略以便于对高压直流输电线路进行更好地保护。 本论文通过对双端双极直流输电系统结构、原理及控制方式等进行分析，利用PSCAD/EMTDC搭建了一个双端双极直流输电系统模型，对该模型提出一种仅需要一端换流站电流数据的新型横差保护方案。该保护方案根据滤波单元特性，利用区内、区外故障时双极信号差值的差异构造区内、区外故障判据，根据区内、区外故障时被保护线路双极信号比值的差异构造故障选极判据，同时满足以上条件则说明发生本极区内故障，保护动作，否则保护不动作。基于上述原理，利用MATLAB对该保护方案进行仿真验证，运用傅里叶算法提取特定频率下故障暂态量信号的实时有效信息，其计算量小，运算速度快。 仿真结果表明：将该保护新方案应用于双端双极系统直流输电线路保护中，能够同时准确识别直流线路区、内外故障和判定故障发生极，当发生本极区内故障时保护能够可靠动作；发生区外故障时保护不动作。该方案原理简单、可靠性高、动作速度快、易于整定，避免了采样过程复杂、通信通道配合难度大等问题，能解决行波保护所不能解决的经高阻接地的直流线路保护问题。该方法仅需要换流站一端的电流数据即可实现直流线路的全线速动，所得到的研究结果对高压直流输电线路继电保护研究提供了较大的实用价值和理论指导。

It's of great significance to research relay protection and fault identification of HVDC transmission line due to the important position of HVDC transmission system in the strategy of global energy internet and relay protection fast, reliable action is crucial for DC system. Usually, the main protection of HVDC transmission line is traveling wave protection and the backup protection are low voltage protection, longitudinal differential protection and so on. We need to develop a new protection strategy for HVDC transmission line for better protection because of such as a series problems incomplete of protection theory, inconsistent of principle, special circumstances(high grounding resistance), inaccurate of fault location and so on. In this paper，I put forward a protection scheme of new transverse differential protection only using single-end converter current data in the model, which is a double end bipolar HVDC transmission system by PSCAD/EMTDC and analyzing the structure, working principle, control mode of two terminal HVDC transmission system. By using the difference between the current subtraction of the two poles, the fault in the region and the outside of the area can be judged, and using the difference between the current division of the two poles, the fault polarity can be judged. Based on the above principle, the protection scheme is simulated and verified by MATLAB. The specific frequency of fault transient signal real-time and effective information extracted by full cycle Fourier algorithm, which obvious brought great convenience to scholar as the advantage of the improved algorithm.，the small amount of calculation and the advantage of fast calculation speed. Simulation results show that when the new protection scheme is applied to the modified bipolar HVDC line protection, it is capable of accurately recognition the internal and external fault and determine the fault pole in DC transmission lines, when the faults break down within the region, the protection can act reliably while external fault occurs the protection do not act. The scheme is simple in principle, with high reliability and fast action, easy to setting, avoiding the complex of sampling process and the difficult problem of communication channel. It can solve the traveling wave protection which cannot be solved by the high resistance connected with the DC line protection. This method requires only at single end of the converter current data which can be realized the speed of DC line across the board, the research results of HVDC transmission line relay protection provides great practical value and theoretical guidance.