This diploma thesis deals with the modeling and parameterization of the electrical system of a pumped storage power plant with variable speed. The system consists of the rigid three-phase balanced grid, the double fed induction machine, which is controlled by the inverter on the rotor side, and the transformer, which adjusts the voltage level of the stator to the inverter. For these components, mathematical models are derived which allow to formulate the losses in a consistent way. Based on specific considerations, in particular for the inverter model, simplified models are developed, which are suitable for the design of control strategies or the application of real-time optimization methods. Furthermore, the models are parameterized and combined to the overall system model. Finally, a comparison of the models with different levels of simplifications is shown in simulation studies.