Abstract: This study carried out an in-depth study and analysis of power losses associated with the Nigerian 330 kV and proposed modifications to the existing network to improve the efficiency, reliability, security and ensure good quality power for the citizenry. The research methodology involved the power flow analysis of the existing network and subjecting it to contingency analysis and simulation using Newton-Raphson method in Power World Simulator (PWS) environment. The study revealed that the existing network cannot cope with contingencies leading to very low performance and even blackout at emergencies. The proposed modifications to the 330 kV transmission network which incorporated some additional lines to form more loops and minimal compensation, meet the acceptable voltage limits of �5%. It also reduces the energy losses from 337.5-189.9 MWH, representing 45% improvement over existing network and enhances reliability and security of the transmission grid.