This paper presents the main features and the use of the security constrained optimal power flow program, called IPSO (Integrated Power System Optimizer), in the electricity market environment. The finding of the optimal power flow solution is realized with the KNITRO solver developed at Ziena Optimization, Inc. The paper emphasizes the original features of IPSO software such as security constrained modeling in both preventive and corrective strategy, the discrete variables modeling, the modeling of units' capability curves, the modeling of the primary active power-frequency control as well as the modeling of the primary active power-frequency control. Finally, is presented the utilization of the SCOPF program to evaluate the steady state TTC (Total Transfer Capability).