Research on the Influence of Three phase Voltage Imbalance on the Low Voltage Side of Ultra high Voltage Single phase Transformers

In order to study the effect of the capacitance difference of single-phase ultra-high voltage (UHV) transformer windings on the three-phase voltage imbalance of low-voltage ungrounded systems, an equivalent model of the power and load characteristics of electrical equipment such as transformers, compensation devices, and measurement devices was established by decoupling the high and medium voltage windings of transformers from the grounding capacity; Comparative analysis of the impact of three-phase voltage imbalance in windings at different positions on ungrounded systems. The results indicate that the voltage balance on the low voltage side mainly depends on the capacitance difference between the main transformer and the low voltage winding, as well as the operating mode of the low voltage side continuously variable transmission. This can be improved by investing in large grounded capacitor continuously variable transmissions or replacing them with continuously variable transmissions of different capacities. Simulation and field experiments have verified the accuracy and practicality of this method.