Contents I. Introduction
When planning a new transmission system, or a system expansion, it is important to think carefully in all the aspects, which can imply in a better performance and also in lower cost. In order to obtain the best cost-performance result, it is important to consider altogether the relevant options and possibilities in the first stages of study, when the basic system conception is defined. In fact, some interesting solutions imply in joint measures and coordinated choices, and can hardly be detected if different aspects are dealt with separately or sequentially, as is done in many system studies. The joint evaluation of different aspects is critical when nonconventional solutions are considered, as is the case of long-distance transmission systems, for which extrapolation of common practice would lead to solutions quite far from optimum. As an example, we present some aspects of a real transmission system-expansion study. This system has some specific constraints, which are summarized as follows.
The previous electric system supplies some small loads.
A new load, which shall be mainly a static load, is located 865 km from the main generation plant.
The load will be 400 MW at the beginning and may increase in the future to 800 MW.
The load shall be attended through a single 420-kV three-phase transmission line.
