对“三道防线”的安全防护体系进行了论述，通过对智能发电、变电、输电、调度、通信及广域测量等智能电网支撑技术的分析，对智能电网新技术条件下“三道防线”进行了扩展。智能预防控制通过“风险预警、预测校核”方式在线优化电网运行方案，将防御体系进行有效的“关口前移”；智能紧急控制通过“在线计算，实时控制”方式实施全局闭环控制策略，电网维持稳定运行能力得到增强；智能恢复控制通过“预设方案、滚动优化”方式加速电网恢复过程，有效减少停电时间和经济损失。

This paper discussed the three-defense-lines of security protection system. The three-defense-lines was expanded under the condition of using smart grid technology, based on the analysis of intelligence support technologies, such as intelligent power generation, substation, transmission, dispatch, communication and the wide area measurement. The technology of intelligent prevention and control could optimize the grid operation scheme with the methods of risk early warning and forecast verification, and made terminal of defense system effectively move forward. The technology of intelligent emergency control could implement the strategy of global closed-loop control with the methods of online calculation and real-time control, which could strengthen the stable operation of power grid. The technology of intelligent restoration control could speed up recovery process of power grid with the methods of default scheme and rolling optimization, which could effectively reduce blackout time and economic loss.