Assessment of Line Overloading Risk for Transmission Networks

Traditional approaches to transmission system security assessment use deterministic criteria e.g. the application of `N-1´ or `N-2´ circuit depletion under prescribed heavy system loading conditions. However, such worst-case deterministic approach does not provide explicitly an assessment of the probability of overloading the system, and the likelihood of the outages is treated equally. Recent research has focused on assessment of the line overloading risk index. This paper aims to extend the evaluation of the line overloading risk index through an extensive systematic evaluation of the steady state performance of the Dubai transmission network under hour-by-hour loading levels over a one year period. Load flow analysis is carried out for the intact system and all N-1 and N-2 contingencies. Over the same annual period, the thermal rating of all transmission lines is calculated, based on a detailed set of local meteorological data. Power flow computations are performed using a commercial load flow program and the systematic multiple study execution and data handling was achieved using a developed C++ based programming code. Over the period studied, the line overloading risk index and the probability distributions of line loadings and ratings is determined.