Abstract: Dongfeng Hydropower Plant has played a role of break point of south power grid and north power grid of Guiyang for ages. In its safety stability device, there is a tactics to treat the “one line tripping and another line overloading” accident of east main double circuit which is very important for thermal stability and safety of 220kV output cables of Dongfeng Hydropower Plant. In 2008, August 29, the east main circuit No.2 tripped, and then the east main circuit No.1 was overload, but the safety stability device of Dongfeng Hydropower Plant didn’t execute the established overload treatment tactics. The reason of the accident and the antiaccident measures were analyzed and introduced, and a proposal about the criterion of relevant tactics for the device was put forward.

Key words: safety stability device, trip, circuit overload, tactics, anti-accident measures