Continuous-Mass-Model-Based Mechanical and Electrical Co-Simulation of SSR and Its Application to a Practical Shaft Failure Event

To accurately evaluate the damage caused by subsynchronous resonance (SSR) to a turbo-generator shaft, we have developed a novel mechanical and electrical co-simulation method, wherein the continuous-mass-model-based mechanical system is simulated in a close-loop or coupled way with the electrical power system so that the detailed torque profile along the shaft can be obtained for further analysis of fatigue loss of life. Nonlinear mechanical damping is also modelled to reflect the torsional inter action more precisely. The co-simulation is implemented using commercial electromagnetic transient program and finite element analysis software. A special dynamic data exchange mechanism is designed to make it proceed very efficiently. As a case study, the proposed method has been applied for the root-cause analysis of a recent shaft failure incident in an India power plant. The extensive simulation results have fully demonstrated its effectiveness in acquiring fine-grained torques and its advantages over previous methods. Finally the direct cause of the shaft failure is identified to be the sustained torsional interaction (one type of SSR) between the turbo-generator and its connected series-compensated power system.