Steady-state security assessment for transmission systems and its application to the Dubai network

Power system security is defined as the ability of a power system to maintain supply without unduly allowing network variables to stray from prescribed ranges. Traditionally, security has been assessed using deterministic criteria e.g. `N-1´ or `N-2´ under prescribed severe system loading levels. However, such worst-case deterministic approach does not provide explicitly an assessment of the probability of failure of the system, and the likelihood of the outages is treated equally. This approach may result in either over or under estimation of system planning reinforcement requirements and, hence, a corresponding excessive or insufficient system security. On the other hand, probabilistic security assessment may offer advantages by considering (i) a statistical description of the performance of the system over an annual cycle together with (ii) the application of historical fault statistics that provide a measure of the probability of faults leading to systems outages. This paper reviews approaches to probabilistic security assessment. Such approaches include (i) identifying various security indices, (ii) reviewing different techniques, (iv) utilizing Monte Carlo simulation, and (iv) integrating deterministic & probabilistic techniques. The application of probabilistic security assessment in real-time operation and system planning is further considered in detail. Preliminary application of the security assessment is presented to the Dubai Electricity and Water Authority (DEWA) transmission network.