The Thumb Loop Project consists of approximately 140 miles of double-circuit 345,000 volt (345 kV) lines and four new substations that serve as the “backbone” of the system. Additional lines and facilities will be needed in the future as wind generators go into service and connect to the backbone system to fulfill the requirements of the state’s Renewable Portfolio Standard. The system is designed to meet the identified minimum and maximum wind energy potential of the Thumb region (2,367 and 4,236 MW respectively) and is capable of supporting a maximum capacity of about 5,000 MW. The new system was constructed in stages. The first segment, the western side of the loop from the Bauer substation in Tuscola County to the Rapson substation Huron County, went into service in September 2013. Phase two in St. Clair County, from the Fitz substation to Greenwood, went into service in May 2014. Phase 3, comprising 56 miles of line in Huron and Sanilac counties and the Banner substation near Sandusky, went into service in May 2015.