Scheduling maintenance activities in an electric transmission system has become a constant concern given the need to perform optimal interventions to extend its use while preserving the reliability of the system, without affecting its availability and stability, and at the same time, reducing its costs and environmental impact. This paper has its inception with a planning strategy defined for this equipment that determines how often each of these required resources should have preventing maintenance in order to properly perform their activities. Having this information as input, a maintenance schedule is planned, considering an estimate of climate conditions, resource availability, the topology of the system and the potential lack of availability of assets that are owned by other companies, but that are connected to the transmission system in site. Following this, an optimization algorithm is presented, inspired in the biology of an ant's colony and integrated with a model of Petri nets with the purpose of finding an optimal solution that includes the decrease of computer analysis time and guaranteeing the fulfilment of all temporary and topological restrictions of the system.