Network Alternatives to Reduce Turbine-Generator Shaft Stresses

Network alternatives to minimize shaft mechanical fatigue due to switching three-phase faults in close proximity of a 1025 MVA turbine-generator connected to a strong 345 kV grid are investigated. The comparative analysis is based on estimated fatigue curves for the major shaft sections, relating maximum alternating torque to fatigue incurred per incident of torsional oscillation. Two half-sized step-up transformers connected to alternate buses, coupled by a bus tie breaker are shown to be effective in reducing such fatigue.