Start-up performance of very large synchronous generators

The requirements for the grid in Germany are increased, since the expansion of renewable energies and the decision to close the nuclear power plants by the federal government. Studies show, that the voltage stability in some areas, during special cases of publishing and load situations, is not guaranteed. In order to build security of supply in a short time, a very large generator of a nuclear power plant, with a rated power of 1.5 GVA, is modified to a synchronous condenser. Because there is no thermal energy from the reactor, the generator cannot start with the steam turbines. It has to be uncoupled from the driving shaft and must start with a converter. The generator and the exciter have a very high mass of inertia. During the starting process it is possible that the rotor begins to run asynchronously, which causes a high thermal loading on sensitive components. By using the method of finite elements this problem is studied in different cases. Another part, which gets observed, is the general behaviour and the electrical and mechanical stresses of the system.