Sensitivity Analysis on Turbine-Generator Shaft Torque in 154kV Transmission System

The torsional stress is caused by interaction between electrical transient air-gap torque by electrical disturbances and mechanical torque of turbine-generator shaft system. If a transient shaft torque exceeds a certain threshold, the loss of fatigue life occurs and in the end it is possible to happen shaft failure. This paper discusses that which factors can damage to turbine-generator shaft and how those factors cause transient shaft torque. For the study, we conducted sensitivity analysis for turbine-generator shaft system to assess torsional stress. We carried out various simulations by using ElectroMagnetic Transient Program (EMTP) based on actual Korea 154kV transmission system. Based on simulation results, this paper provides Zone of Vulnerability (ZoV) considering fault types and locations. Therefore, system operators need to study those factors that may result in torsional stress in detail, especially within ZoV.