A computer program for transient analysis of steam turbine generator overspeed

Abstract

One of the most important conditions for safe turbine generator operation is protection against turbine overspeed. A mathematical model is presented which enables the analysis of transient processes with variable revolutions of a turbine-generator following the disconnection of the generator from the electrical grid. The model provides the capability to generate an arbitrary turbine generator system through input data and to simulate system behavior in time. The main building blocks of the model include high and low pressure turbines, a moisture separator, a reheater, a condenser, feedwater heaters, a deaerator, pumps, and control valves. The model is built on the lumped-parameter approach. The turbine-generator system is described by a set of control volumes interconnected by junctions. Control volumes are represented by time dependent energy and mass conservation equations; junctions are described by quasi-steady momentum equations. The overall approach of the model is demonstrated for a 220 MWe steam turbine for nuclear power plants. The model description is concentrated primarily on the turbine generator. Comparison of the model with experimental data obtained for a 220 MWe turbine shows very good agreement.