Identifying Operating Parameters of Synchronous Generator that are the Most Sensitive to Impacts of Quasi-Constant Currents on Unit Transformer

The authors developed an assessment procedure for the operating parameters of the synchronous generator taking into account the saturation of the unit transformer core under quasi-constant currents occurring during geomagnetic disturbances. They identified the dependencies between the full power, stator current, synchronous EMF, and the load angle of the synchronous generator, and the quasi-constant current over ranging from values that are nearly 2 times less than the idling current of the unit transformer to those that are almost 1.5 times over the rated current of the high-voltage windings of the unit transformer. Based on the TVV-320 turbine generator/TDTs-400000/242/20-unit transformer module, the authors rationalize the use of linear approximation of the dependencies between the synchronous generator full power and stator current and the quasi-constant current under constant load with active power and constant voltage in generator buses. A quantitative measure is suggested for the sensitivity of full power and stator current to the impact of quasi-constant currents on the unit transformer. The authors demonstrate the non-linear character and interdependence of changes in the synchronous EMF and the load angle under the constant active power and quasi-constant current impacts on the unit transformer that facilitate the improvement of the static operational stability of the synchronous generator.