A wind energy installation test device for defined production of grid system faults, and a method thereof. The test device can include an output configured to connect to a wind energy installation, an input configured to connect to a grid system, and a switching device for connection of an electrical disturbance component relating to a grid system parameter. An autotransformer can be used for the electrical disturbance component. The grid system in a sound state can be connected to a primary winding connection and the grid system in a disturbed state with respect to the grid system parameter can be output at a secondary winding connection.