EFFECT OF HVDC LINE FAULTS ON TRANSIENT TORSIONAL TORQUES OF TURBINE-GENERATOR SHAFTS

This paper investigates the effects of HVdc line faults, line de-energization, and line re-energization on the transient torsional stresses of steam turbine-generator (T-G) units. The studies are conducted on a bipole HVdc system which connects a T-G set to a large ac system. The shaft transient stresses of the T-G set as a result of HVac line fault, fault clearing, and automatic reclosure are also determined when the HVdc transmission system is replaced by an equivalent double-line HVac system. The EMTDC program is used for the simulation studies. The studies conclude that transient shaft stresses as a result of HVdc line fault and its subsequent switching events are (1) significantly less severe than those of HVac faults and subsequent switchings, and (2) not sensitive to the fault location and disturbance duration.