This paper presents a hybrid algorithm using a Hybrid Firefly and Particle Swarm Optimization (HFPSO) algorithm to determine the optimal placement of SSSC devices. A multi-objective function is used to increase voltage stability, voltage profile and minimize overall power losses of the transmission system. At first, PSO algorithm is used to find the optimal SSSC location and further more to reduce the power losses and voltage profile enhancement to overcome the sub-optimal operation of existing algorithms. The HFPSO algorithm is used to determine the optimal placement of SSSC series FACTS device and verification of the proposed algorithm was achieved on standard IEEE 14-bus and IEEE 30-bus transmission systems in the MATLAB environment. Comprehensive simulation results of two different cases show that the proposed HFPSO demonstrates significant improvements over other existing algorithms to enhance voltage stability and reducing active and reactive power losses in electrical power transmission systems.