The grid is made up of small distribution lines and large transmission lines like this. The transmission grid is analogous to an interstate highway system for electricity. The Midwest Independent Transmission System Operator, Inc. (MISO) plans and operates this interstate highway for electricity. PPI, a generation and transmission co-op serving the generation and transmission needs of 10 central Illinois distribution co-ops recently joined MISO. Being a MISO transmission owner will ensure the co-op has a say when it comes to the planning and operations of the transmission grid.