The distribution feeder design refers to how distribution feeder lines are laid out and interconnected to provide service to customers, and there are several options. A network system connects multiple primary feeds and interconnects multiple distribution circuits in the form of a grid. While network systems provide the highest form of reliability since customers can be served in multiple ways, they are also expensive because of the costs of duplicative equipment, transformers, and specialized network protective equipment. Networks are generally used in downtown urban areas with highly dense critical loads.