Distributed remedial action strategy for a 500-kV AC transmission system

Generally, EHV transmission system reinforcement is unable to keep pace with developments at the generation level, which are subject to manifold uncertainties, especially in deregulated markets. Where there is a significant time gap between network developments and generation developments, it is necessary for the power system to be operated during peak load in an “alert” state, which conflicts with basic security rules, such as single contingency withstand. Among the lines of defense for avoiding further supply deterioration are event- or response-driven distributed Remedial Action Schemes (RAS), which are activated from the system control centers if the power flow on a transmission line section exceeds a predefined critical value. RAS can be practically implemented faster than a fully fledged Static and Dynamic Security Assessment embedded in the real-time environment of the Energy Management System, and are at the same time a wholly satisfactory solution for simple transmission system configurations. The paper presents the study methodology and conceptual design for distributed RAS projects currently under implementation in two similarly structured 500-kV power systems in developing countries.