In this article, the primal-dual interior-point methods are used to minimize costs and losses in a predispatch model for the generation and transmission of direct current (DC) power flow in a hydroelectric system with pre-programmed manipulations; i.e., in cases of preventive maintenance, within a period of twenty-four hours. From the computational standpoint, the effort required to solve a problem with and without manipulations is similar, and the reasons why will be also discussed in this study. Computational results prove these findings.