Abstract
<title>Abstract</title> <p>Shared-right-of-way (SROW) corridors between 750 kV UHV transmission and 35 kV distribution lines are prevalent in Northwest China. The resulting three-phase voltage unbalance in distribution lines threatens power system reliability. This paper proposes a mechanism analysis method based on multi-conductor system capacitance matrix unbalance theory. By deconstructing capacitance matrices, the mechanism of zero-sequence voltage rise due to geometric asymmetry under strong electric field coupling is investigated. Capacitance matrices are extracted via finite element method (FEM). A line model incorporating distributed parameters and asymmetric coupling is developed to quantify the impacts of coupling distance, length, ratio, and load on zero-sequence voltage unbalance. Results show that unbalance decreases as distance increases, significantly beyond 100 m, but increases with coupling length and ratio. Loading causes the unbalance to drop sharply and stabilize after 200 kW. Furthermore, a BP neural network model using these factors yields a test correlation above 0.998 and an average relative error within 1%. This research provides an efficient assessment tool for the engineering design of SROW power lines.</p>