ABSTRACT: This paper presents a methodology for the optimal location of distributed generation (DG) in power systems using the Weighted Transmission Loading Relief (WTLR) nodal indexes. These indexes are used to guide a GRASP metaheuristic in charge of the optimal allocation of different DG units in a transmission network. The objective consists on minimizing the most negative WTLR indexes, which results in an increase of the system security. Several tests are presented in a representative prototype of the Colombian power system, evidencing the effectiveness of the proposed methodology. Results show that a proper allocation of DG units minimizes system overloads both in normal operation and under contingencies.COL0010477