Geographically speaking, power systems are probably the largest interconnected networks in service today and offer interesting engineering challenges. Generating sites are far away from big load demand regions. Some power plants are close to natural resources, while others are in areas with fewer e1nvironmental restrictions. Because of this generation/load separation, a reliable power transmission network is necessary. Right-of-way restrictions limit transmission line construction. In general, almost nobody wants to live close to a power plant or a transmission line. This limited network growth requires optimization of available resources.