Applications for Phase-Shifting Transformers in Rural Power Systems

The use of phase-shifting transformers (PST) to control real power-flow can take advantage of financial incentives, meet contractual import or export obligations, or prevent exceeding line rating constraints. Millennium Challenge Account Nepal (MCA-N) requested that a PST be sized to control powerflow at the India-Nepal border. MCA-N desired the analysis of off-peak scenarios that were not represented in the two base cases provided for the project. The provided base cases were used to create a study case representing the desired power-flow conditions. This paper first provides a summary of PST theory and design, then various methods of specifying the phase-shift and through power rating of a PST are explored. This involves the capacity to prevent the simultaneous import and export of real-power by one balancing authority. A method of modeling a PST in PSS/E is also described, as well as a case creation method for a loop-flow scenario. This paper concludes with the sizing methodology chosen by the authors, along with a technical explanation. As a case study, a feasibility study between Nepal and India is analyzed.