The members， working groups， technical reports and annual meeting arrangement of CIGRE SC B5 are introduced firstly. Impact of IEC 61850 on both protection and automation protection systems and substation automation for major disturbances are selected as the preferential subjects of the SC B5 in the 2006 session. More and more substation automation systems based on IEC 61850 have been in service nowadays， and the obtained installations and experiences are introduced therein. Rational topology of power grid and layout of substations， perfect protection system and indispensable stability control equipment are the effective means to deal with major disturbances and avoid blackout in a large area. The validity of original“three defense lines” in China power grids is further proved with the discussion during the session.