A simulator has been designed for the training of power system operators, which allows the operator to practise all facilities which are provided in the control center, without interfering with the power system itself. Furthermore, he can be trained to handle emergency situations which will be initiated by a so-called event simulator. This training simulator makes full use of the existing software and computer facilities already provided in the dispatch center. The design criteria for such a simulator are stated and its modular structure is explained. The interactions between the different models and the data flow is described