This Paper presents an approach to solve the single objective optimal power flow problem considering the critical objective function of minimization of sum of squares of voltage deviations from desired voltages at all load buses while satisfying a set of constraints associated with the control variables such as generator excitations, tap positions of on-load tap changing transformers and switched var compensators and also dependent variable reactive power generation of all generators. This problem has been solved by using the Particle Swarm Optimization (PSO) method and the results obtained from this proposed method have been compared with the results obtained by the conventional Non-Linear Programming interior point method(NLP). To test the effectiveness of the proposed method, the results are obtained for a practical 24 bus EHV southern region equivalent Indian power system network. Analysis of results including effect on power loss, voltage stability indices as well as sum squared voltage deviations are done and superiority of the proposed method in comparison to NLP method is demonstrated.