1. A test apparatus for testing a wind turbine installation with a control system in respect of riding through a voltage dip, comprising: a measured data capture unit with an interface for connection to the control system of the wind turbine installation and for capturing measured data from the control system, a measured data converter connected to the measured data capture unit in order to receive the captured measured data, which combines the captured measured data to form a standardized measured dataset, and an analysis unit connected to the measured data converter in order to receive the measured dataset, the analysis unit further comprising: a rule memory, in which calculation rules for calculating the values of particular variables from the measured dataset are stored, a requirements memory, in which permitted values for the particular variables are stored, a criteria memory, in which evaluation criteria are stored, a calculation unit connected to the measured data converter and the rule memory, which derives values for the particular variables from the measured dataset, a comparison unit connected to the calculation unit and the requirements memory, which compares the values derived for the particular variables with the permitted values contained in the requirements memory, an evaluation unit connected to the comparison unit and the criteria memory, which performs an evaluation of the comparison in accordance with the evaluation criteria and keeps the result of the evaluation ready for output.