The optimal operation of a power system in both normal and contingency cases has a significant role in the power system operation. To guarantee a system to operate securely in both cases, the most severed case should be included in the optimal reactive power dispatch (ORPD) problem. The objective of the SCORPD problem is to solve the ORPD problem in both normal and contingency cases so that the total power loss, stability index, or voltage deviation is the system is minimized satisfying all unit and network constraints. In this article, a hybrid particle swarm optimization and differential evolution (HPSO-DE) is proposed to solve this SCORPD problem. The proposed method is a combination of PSO and DE methods to utilize their advantages so that the search ability of the method can be enhanced. The proposed method has been implemented on the IEEE 30-bus system for different objectives with different scenarios. The obtained results have been indicated that the proposed HPSO-DE method can be very effective for dealing with the complex and large-scale SCORPD problem