In this paper, an optimization process based on the application of the Tabu Search is developed, in order to expand electrical networks by searching the topology that minimizes the voltage sag/year number in the electrical system. A case study is presented, in which a static transmission expansion planning in an IEEE test system is addressed, in order to demonstrate the application of the developed methodology.Keywords-Network expansion, power quality, tabu search, voltage sags (dips).
I. INTRODUCTIONThe demand of electricity has been increasing over the years. For this reason, the expansion of electrical networks is necessary, and efficient and reliable construction techniques are required. These techniques must be consistent with the competitive environment of the current electricity market.The objective of the network expansion planning consists in determining an (optimal) expansion plan for the electric network with circuits that satisfy the operational requirements for a forecasted demand growth [1]. Basically, the problem to be addressed is how to minimize the cost of the expansion network, maintaining a certain level of reliability [2]-[6].The network expansion, both at distribution and transmission level, may be studied using static or by dynamic models. A static model tries to answer questions like where and which type of new circuits should be built in an optimal way planning horizon. A dynamic model tries to answer the same questions but, in addition, answers the question of when to add new circuits. In other words, the dynamic model considers several horizons in the same issue [1] [7].On the other hand, in the past, both aspects of operation and planning were in the hands of centralized institutions. Today, the separation of the electricity business has created new challenges in the restructuring industry that must be faced. The restructuring of the electricity industry has resulted in the appearance of new actors, such as traders and independent power producers, which make the expansion planning more difficult [2] [8].Moreover, the electricity market deregulation has led to an increased need for quality indicators, in order to be more competitive and to attract end-users which are demanding higher levels of power quality that is related to electrical