Introduction Power system not only needs to be economic, but more needs to be secure. System security:the system can continue to be in normal operation state after some devices get faulted. How to guarantee (enhance)system security? o Reserve Enhance the reliability of the devices Operator's decision making 电力拿镜广城洲量写控制四川省童点实验蜜 家电电力系统广域测量与控制四川省重点实验室 Introduction  Power system not only needs to be economic, but more needs to be secure.  System security: the system can continue to be in normal operation state after some devices get faulted.  How to guarantee (enhance) system security?  Reserve  Enhance the reliability of the devices  Operator’s decision making