Phase-Coordinate Modeling of Electromagnetic Transients for Fault Analysis in Distribution Networks

Abstract

Single-line-to-ground (SLG) faults in medium-voltage distribution networks can produce significant capacitive currents and transient overvoltages, particularly in cable-dominated networks with different neutral-grounding arrangements. This study develops a phase-coordinate modeling framework for three-phase distribution networks based on discrete multipole models and the second-order implicit Gear method. Transmission-line sections, transformer windings, and shunt elements are represented in a unified current-based form and assembled into a nodal system. The model was implemented in software and evaluated using a 110/6 kV network section of an operating substation, with calculated transients compared with field-recorded oscillograms. The model reproduced the main features of the measured SLG-fault response, including capacitive-current impulses and transient overvoltages. Arcing faults produced overvoltage factors of 2.1 during arc extinction and 2.4 during subsequent restrikes. Parametric analysis showed that neutral-reactor tuning strongly affects the reactive component of the SLG-fault current and the neutral displacement voltage near resonance. The framework provides a basis for transient analysis, assessment of neutral-grounding measures, and further studies of overcurrent and overvoltage protection.