Regional Power Grid Security Technology

Regional power grid(RPG) is the foundation and premise in interconnection of power grids across the whole country. When oscillation occurs in interconnected power grid owing to big disturbance, if there are no effective measures to identify and control, the oscillation will spread and result in large scale blackout. So it is very important to research the technology on RPG's security protection, among the main research contents, out-of-step islanding control and restorative control after the fault are two crucial contents. Islanding system in the proper place can split the out-of-step system into some irrelevant subsystems effectively, meanwhile every subsystem should be ensured to run stably. While restorative control after the fault can ensure the whole power system to run again integrally. In addition, the application and development of Safety&stability control system is also deserved research.This paper firstly analyzes the characteristics of cross-section of transmission line and its function in interconnected power system. Based on the transient stability of cross-section of transmission line both in one RPG and between two RPGs, this paper also introduces the idea that can realize security protection of RPG Through analyzing the change character of every variable of state during the process of out-of-step action happened among RPGs, it proposes an out-of-step islanding criterion which is based on power flow and power balance of cross-section of transmission line. As a result, islanding control can be realized by using it as the start-up criterion of islanding when out-of-step happpens. The simulation on ten machines testifies the validation of the proposed method. Then, it takes the research on restorative control strategy on Guizhou power grid for example and proves that using cross-section of transmission line as the object of both islanding control and restorative control is practicable. Finally, the scheme on central-controlled Safety&stability control system used in interconnected power grid is put forward. Whereafter it shows its practicability by taking Guizhou power grid for example. Furthermore, the paper also proposes a new viewpoint about the combination of Safety&stability control system and digital power system(DPS).