Impact of Pairwise Choice of Transformer Tapchanger Settings in Large Interties on Grid Efficiency

In transmission and distribution networks, lines are employed to link various regions, enabling the exchange of active and reactive power. When interties are constructed at a higher voltage than the connected networks, step-up and step-down transformers are needed at the ends of the intertie. In this paper, the authors examine whether the combined settings of the transformer tap changers at these ends can influence the power flow in the intertie and, more significantly, affect the power system's efficiency, as measured by the total active power system losses and the related life-cycle costs. The investigation results revealed that the selection of tap changer settings in pairs can, firstly, significantly impact the distribution of power between the intertie and the rest of the system. Secondly, it can determine the system’ s efficiency, as indicated by the amount of total active power losses. It can significantly impact the life-cycle cost of active power system losses. Therefore, the settings of the tap changers on the intertie transformers should be chosen with due consideration of the potential techno-economic effects these choices may have.