JPS_V4_N2_RP5 P. Balachennaiah M. Suryakalavathi Journal on Power Systems Engineering 2322–0376 4 2 46 63 Firefly Algorithm (FA), Optimal Power Flow (OPF), Continuation Power Flow (CPF), Interior Point Successive Linear Programming (IPSLP), Real Coded Genetic Algorithm (RCGA), Unified Power Flow Controller (UPFC) In this research work a meta-heuristic algorithm known as Firefly Algorithm (FA) is used for optimizing the control variables for simultaneously optimizing the transmission system's Real Power Loss (RPL) and Voltage Stability Limit (VSL). Mathematically, this problem can be expressed as nonlinear equality and inequality constrained optimization problem having an objective function with the integration of both RPL and VSL. Transformers taps, Unified Power Flow Controller (UPFC) location and its parameters like series injected voltage magnitude and phase angle of UPFC are incorporated in the form of control variables during the formulation of the problem. The effectiveness of the proposed algorithm has been verified on IEEE 14-bus system. Simulation outcomes received with this new FA algorithm have been compared with the Real Coded Genetic Algorithm (RCGA) for the single objective of minimization of RPL and multi-objective with respect to RPL minimization and VSL maximization. In this paper Interior Point Successive Linear Programming (IPSLP) technique is also considered for the single objective of RPL minimization to compare with the FA technique. The simulation results show the effectiveness and also the superiority of the FA with regard to optimizing both RPL and VSL. May - July 2016 Copyright © 2016 i-manager publications. All rights reserved. i-manager Publications http://www.imanagerpublications.com/Article.aspx?ArticleId=8134