A compact algorithm for the steady-state security assessment of power systems

Security assessment is selected as one of the aspects of power system operation in most need of improvement and best suited to improvement through the use of emerging compact algorithm technologies. This paper examines some of the issues involved in actually making these improvements. The on-line steady-state security analysis of a power system requires the evaluation of the effect of all possible contingencies on the system. The traditional approach to security analysis is to test all contingencies sequentially to evaluate system performance and reliability by simulating outages of one or more generating units and transmission lines to investigate their effects on bus voltages and line power flow. In this paper, a mathematical algorithm suitable for addressing the steady-state assessment of a power system using the DC load flow technique is derived. A compact algorithm, using a reduced matrix order, has been implemented, which reduces the computation time enormously. The technique assumes that the part of the system far from a contingency is only slightly affected by the contingency or is not changed. For each contingency, the system is decomposed into three tiers, resulting in a subsystem of smaller size. The compact algorithm is applied to this subsystem to evaluate the power flow in the lines of the subsystem. The results of this proposed technique have been compared with those obtained from the standard DC load flow for the whole system and are found satisfactory within an acceptable range of accuracy with a reduction in the computation time. The IEEE 30-bus power system model was used to evaluate the algorithm.