These permitting regulations refer to the minimum distance the tips of the blade must be above the ground or other nearby obstacles. This ensures both safety for structures and beings near operating turbines, as well as promoting the most efficient use of the wind resource.
Permitting requirements for safety equipment generally refer to the presence of braking systems in the event that the rotor spins too fast in high wind or to help prevent a catastrophic failure. Most modern turbines today include, in the technology design, both automatic and manual braking options to slow or stop the rotor altogether.
Proposed wind energy projects in Minnesota with a total nameplate capacity of 5MW and greater are subject to state regulation while projects under that threshold are subject to local regulation. For more information about the state permitting requirements and process, visit MN Public Utilities Commission.