TRANSIENT TORSIONAL TORQUE STRESSES REDUCTION ON TURBINEGENERATOR SHAFTS BY SIMULTANEOUS AC-DC POWER TRANSMISSION
This research paper investigates the effects of line faults, line de-energization and line re-energization on the transient torsional stresses of steam turbine-generator (T-G) units in simultaneous AC-DC transmission system. The concept of damping the transient torsional torque stresses excited due to line faults by utilizing fast controllability and modulation of dc component in simultaneous AC-DC power transmission is also demonstrated. The studies are conducted on a simultaneous AC-DC line system which connects T-G set to a large ac system. For the purpose of comparison the simultaneous AC-DC power transmission system is replaced by an equivalent conventional AC system and performances are evaluated. The studies conclude that transient shaft stresses as a result of simultaneous AC-DC line fault and its subsequent switching events are significantly less severe than those of conventional AC line faults and subsequent switching. PSCAD/EMTDC software is used to carry out for simulation studies.