This paper presents an algorithm for the control of bus voltage and generator reactive power in an electricity supply system. Classic solution methods such as linear programming make use of linear approximations of system equations and as such have a limited precision. Genetic algorithms, connected to standard load flow calculations, do not need such approximations and are capable of finding numerous solutions for the emergency control of disturbed bus voltages. The disadvantage of GA's is the heavy computational burden. The paper presents a way of combining the benefits of linear approximation and a genetic algorithm into a solution method for the minimum number of control actions possible. The algorithm was demonstrated on a 300-bus model of the Israel Electric network.