Simulation and Analysis of Transformer Tap Changer Settings for Voltage Regulation in Electrical Distribution Systems

Abstract

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Transformer tap changers are widely used in power distribution systems to regulate voltage levels and maintain acceptable operating conditions. This study evaluates the effect of transformer tap position adjustment on the voltage profile of a distribution network using load flow simulations in ETAP 19.0.1. Five tap settings were analyzed: −5%, −2.5%, 0%, +2.5%, and +5%. The results show that tap variations have little influence on the primary-side voltage, with Bus3 remaining nearly constant at 19.68–19.70 kV (98.4–98.5% of nominal voltage). In contrast, significant changes occur at the medium- and low-voltage buses. The −5% tap setting provides the best voltage profile, producing 3.63 kV at Bus4 (100.8%) and 0.395 kV at Bus5 (98.8%). At the nominal tap position, voltages decrease to 3.45 kV and 0.375 kV, indicating moderate undervoltage conditions. Further increases in tap position lead to lower voltages, with the +5% setting resulting in the poorest performance, where Bus4 and Bus5 fall to 3.28 kV (91.1%) and 0.357 kV (89.3%), respectively. These findings indicate that lower tap positions improve voltage regulation by compensating for voltage drops caused by load demand and feeder impedance. Therefore, the −5% tap setting is identified as the optimal operating condition for maintaining voltage levels within acceptable limits while improving power quality and system reliability.