⁹Directional relays are useful for protecting electrical generators susceptible to acting as a motor and drawing power from the network rather than delivering power to the network. Generators driven by wind turbines are an example of this class: even a relatively small amount of power flowing in reverse direction (from the grid to the generator, “motoring” the generator) is undesirable, and so it is wise to isolate a “motoring” generator based on a much lower current than what would be considered unacceptable in the generating direction. A regular 50 or 51 overcurrent relay cannot discriminate between the two directions of power flow, but a 67 overcurrent relay can.