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Under overload conditions, corrective actions must be carried out in a short time in order to avoid blackouts. However, the control of system facilities in the new market environment has changed the standard overload relief procedures, resulting in high costs for the transmission system operator. To address this issue, an overload relief procedure based on reactive power control applicable to small disturbances is presented. Corrective actions are determined by linearizing the system parameters around the initial operating point in order to calculate the minimum cost for every possible combination of the selected reactive devices. The local nature of reactive power allows us to reduce the set of devices to be used, which speeds up the process and make it suitable for real-time applications. An analysis based on cooperative game theory solutions illustrates the economic aspects of the proposed procedure. Extensive tests have been conducted with the IEEE 118-bus test system and with the Interconnected Brazilian System (SIN), in which a real situation that took place in the summer of 2006 is presented, and proper conclusions are derived.