The simplified model illustrates possible physical limitations to the reliable and economic flow of power that can evolve over time as the system changes. These subareas form a simplified model of load areas connected by the major transmission interfaces across the system. NB includes New Brunswick, Nova Scotia, and Prince Edward Island (i.e., the Maritime provinces) plus the area served by the Northern Maine Independent System Administrator (USA). NB, HQ, and NY = New Brunswick (Maritimes), Hydro-Québec, and New York external balancing authority areas.RI = Rhode Island/bordering Massachusetts.SEMA = Southeastern Massachusetts/Newport, Rhode Island.CMA/NEMA = Central Massachusetts/ northeastern Massachusetts.Boston (all capitalized) = Greater Boston, including the North Shore.VT = Vermont/southwestern New Hampshire.NH = Northern, eastern, and central New Hampshire/eastern Vermont and southwestern Maine.ME = Western and central Maine/Saco Valley, New Hampshire.The ISO has also established 13 subareas of the region’s electric power system, which are shown here along with the three neighboring power systems: