变电站继电保护在功能上分为主保护与后备保护，主保护能够快速的切除故障元件，而传统的后备保护存在动作延时长、整定配合困难、容易引起连锁跳闸事故的缺陷。因此，有必要针对后备保护展开分析和研究。智能变电站利用数字化技术和网络技术实现信息的数字化、标准化、规范化、标准化和全站信息的共享化。基于智能化变电站全站信息共享的集中式后备保护为解决传统后备保护的问题提供了新的思路。 针对传统后备保护的缺陷，在智能变电站全站信息共享的基础上，采用了传统主保护加集中式后备保护的保护配置方案。这种配置方案既能发挥传统主保护的优势，又充分利用了智能变电站信息共享的优势，针对变电站内一次设备配置集中式的后备保护，对后备保护进行了优化，有利于提高保护性能。 研究了基于方向比较原理的集中式后备保护算法。首先根据方向元件与一次设备的连接关系形成一次设备/方向元件关联矩阵，其次根据方向元件的输出值完成矩阵的赋值，根据赋值之后的关联矩阵计算一次元件的故障方向综合值，然后确定判据及门槛值，实现故障元件的准确识别。算例分析结果表明该算法能够准确识别故障元件。 研究了基于差动比较原理的集中式后备保护算法。算法定义了不同的差动区（边界差动区、站内差动区、元件差动区、搜索差动区）。首先根据边界差动区和站内差动区的不同特点，区分站内元件故障或线路故障。当确认线路故障后，启动搜索差动区判断发生故障的线路。当确认站内元件故障后，查看元件差动区判断发生故障的站内元件。并分析阐述了差动电流的计算方法及仿真过程中不平衡电流产生的原因。最后利用PSCAD仿真软件做了大量的仿真实验，实验结果表明该算法能够准确的识别故障元件。

Substation protection has relay protection & back-up protection based on the function. Relay protection can remove faulty components quickly. Traditional backup protection has shortcoming such as long delay action, tuning difficulties, prone to tripping accidents chain, so it is necessary to analyze and study for backup protection. Intelligent substation using digital technology and network technology can get digital standardization information and share the information on whole station. Intelligent Substation Based on information sharing, centralized backup protection for solving the problem of traditional backup protection provides a new way of thinking. To solve traditional backup protection’s defects, based on Smart Substation information sharing use the traditional primary protection plus protection configure ration centralized backup protection. This configuration can not only play the advantages of the traditional primary protection, but also makes full use of the advantages of intelligent substation information sharing. Once the device is configured for centralized backup substation protection, the backup protection is optimized, helping improve protection. Study the algorithm based on the comparison of direction. According to the connections of the direction elements and primary equipment, to form the direction matrix is also important. Complete of the assignment matrix based on the output value of the directional element, Determine the threshold criterion and accurate identification of faulty components. Finally, specific examples (a device put into operation substation and substation equipment fault identification quit running in both cases), numerical results show that the algorithm can accurately identify the faulty component. Study the centralized backup protection algorithm based on the principle of differential comparator. The algorithm defines the different zones of differential (differential zone boundary、the station of the differential area、 the element of the differential area & the search differential zone). Firstly, according to the different characteristics of the border area and the station differential zones, distinguish the station component failure or line failure. When the confirmation line is fail, start the search area to determine the differential fault lines. Also, when the confirmation station component is fail, we need checking components area to determine the fault station component. Finally, a lot of simulations using software PSCAD simulation experimental results show that the algorithm can accurately identify the faulty component.