摘要:结合传统继电保护的设计思想和技术方法，对一段电网进行分析，根据继电保护整定原则求取所需零序电流保护和距离保护的整定值，用于PLC实现电力系统继电保护。PLC代替机械触电继电器，通过软件编程，用内部逻辑关系代替实际硬件接线，内部继电器动作时间几乎为0，改善了装置的动作准确性和可靠性。根据PLC所能识别的信号，将电网信号转换成PLC能识别的信号，读入PLC进行处理；结合阶段式零序电流保护、阶段式距离保护、重合闸保护装置原理，应用PLC编程软件实现一系列的保护功能。

关键词： 继电器；零序电流保护；距离保护；重合闸；PLC

Abstract:Combined with the design idea and technical methods of the traditional relay protection design idea and technical methods, and analyzed a power grid, According to the relay protection setting principles for calculating the zero sequence current protection and distance protection to set the values. The values will be to use for the PLC to design the power system protection. PLC instead of mechanical shock relay, and use the software of the Internal logical relationship programming, t o instead of practical hardware connection. The action time of PLC is almost zero, so PLC could improve the accuracy a reliability of the action of the device. According to the signal which PLC could identify, we need change the signal of power grid for the PLC, to make it could be identified by the PLC. Combined with the principle of stage type zero sequence current protection, stage type distance protection, auto-reclosure, to realize the function of the principle of stage type zero sequence current protection, stage type distance protection, auto-reclosure with PLC.

Keywords: relay; zero sequence current protection; distance protection;auto-reclosure; PLC

　　　目前，各地供电部门将变电站自动化作为当前电网改造的一项重要指标，要求变电站的继电保护装置不仅仅是分散保护和控制相应的对象，还必须将各个保护对象和保护装置本身的运行状况、故障性质、参数设置及相互关系等综合起来构成一个完整的信息显示和信息处理系统，便于全站集中管理和远方监控。

　　　可编程逻辑控制器的主要特点是：用内部已定义的各种辅助继电器代替机械继电器，通过软件编程方式用内部逻辑关系代替实际的硬件接线。这些辅助继电器的节点变位时间近似于0，可不考虑机械继电器的返回系数。通过PLC的优点，可对继电保护系统进行优化，增强装置的动作准确性和可靠性。PLC的通讯装置使得个保护装置之间、装置与主控机之间能够按计算机通讯方式进行数据传递，通过监控主机，可构成一个自动化的变电站。