Abstract
Subsynchronous oscillation (SSO) fault can cause torsional vibration and fatigue damage of the shafting system, thereby endanger the safe operation of the turbo-generator set. A novel framework for the online evaluation of shaft fatigue damage suffered from SSO is proposed in this paper. The main ingredients of the framework are a calculation method of the turbo-generator shaft torque, rain-flow counting method, S-N curves and linear damage accumulation law. The shaft torque calculation method, based on the measured torsional angle and generator voltage and current data, is mainly discussed. The effects of damping and electromechanical coupling under complex operating conditions are included in the measured data, and the calculated results of the torque are accurate. The novel framework was used to evaluate the fatigue damage of a 1000 MW turbo-generator shaft that suffered an actual SSO fault caused by a high-voltage direct current (HVDC) transmission system and some meaningful conclusions were given.
Highlights
The turbine-generator shafting system has significant elasticity, and torsional vibration fault may occur if electromagnetic and steam moments are not balanced under certain conditions
A novel framework for the online evaluation of fatigue damage of turbo-generator shaft caused by Subsynchronous oscillation (SSO) in power systems is proposed to overcome the deficiencies of the existing methods
We focus on the stress-based approach which is improved for torsional fatigue damage evaluation in this paper
Summary
The turbine-generator shafting system has significant elasticity, and torsional vibration fault may occur if electromagnetic and steam moments are not balanced under certain conditions. A novel framework for the online evaluation of fatigue damage of turbo-generator shaft caused by SSO in power systems is proposed to overcome the deficiencies of the existing methods. An accurate method is proposed to estimate torque in weak sections in real time based on the measured torsional angle and generator voltage and current data, which already include the influence of the effects of the system damping and the electromechanical coupling under complex operating conditions. The fatigue damage of an actual on-duty 1000 MW turbo-generator shaft caused by SSO is evaluated by use of the proposed torque calculating method, rain-flow counting method, S-N curves and linear damage accumulation law. The S-N curves used in the paper are reasonably improved on the basis of the S-N curves provided by the manufacturer
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