<![CDATA[The 150 kV Ngimbang–Babat–Lamongan transmission line is a vital part of the East Java power system. PT PLN has carried out reconductoring on the Babat–Lamongan and Lamongan–Cerme lines, which altered the line impedance parameters. These changes potentially cause inaccuracies in the operation of distance relays if the settings are not adjusted accordingly. This study aims to analyze the impact of reconductoring on distance relay settings, compare them with previous settings and IEEE standard-based calculations, and ensure selective coordination among relays. The methodology involves comparing distance relay settings before and after reconductoring, as well as calculating the settings for three protection zones (Z1, Z2, Z3) based on line and transformer impedance data, followed by coordination simulation using ETAP 20.0.0 software. The results show that the Babat–Lamongan distance relay settings before reconductoring differ significantly, by up to 9.26% from the post-reconductoring and calculated results, indicating the importance of resetting the distance relay after any impedance change. The post-reconductoring Babat–Lamongan settings are ideal, with less than 5% deviation from the calculated values and no overlapping detected. Conversely, the Ngimbang–Babat distance relay settings are no longer suitable, as Zone 1 covers only 72.84% of the line (below the IEEE standard of 80%), and Zone 2 remains irrelevant after reconductoring due to outdated parameters. This study recommends new settings for the Ngimbang–Babat relay: Z1 = 4.6128 Ω, Z2 = 6.9192 Ω, and Z3 = 23.6631 Ω, which have been validated through ETAP simulations to ensure selective and reliable coordination.]]>
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