열화에 따른 바리스터의 고조파 및 비선형 특성에 관한 연구 = A Study of Varistor Harmonics and Nonlinear Characteristics According to Degradation

다국어 초록 (Multilingual Abstract)

This study aims to investigates the effects of degradation on the harmonics and nonlinear characteristics of Metal Oxide Varistors (MOVs), which are surge protection devices (SPDs) installed to prevent damage to electrical equipment caused by lightning-induced surges. The physical changes to MOVs under accelerated degradation and gradual voltage ramping were analyzed using Megger S1-1568 and Hipot Analyzer 19055-c. Accelerated aging tests were conducted by applying voltages at 10-hour intervals with leakage currents of 3mA, 4.5mA, and 6mA, for a total of 50 hours to simulate different degrees of degradation. As degradation progressed, both odd harmonics and even harmonics were generated. Initially, the Total Harmonic Distortion (%THD) increased due to degradation, but as the degradation intensified, %THD decreased due to the overall increase in leakage current outweighing the increase in even harmonics. Furthermore, the magnitude of the nonlinear coefficient significantly decreased with the progressing degradation, from 72.67 to 21.79 (at 3mA), 19.95 (at 4.5mA), and 2.52 (at 6mA). By continuously monitoring the physical changes, such as the generation of even harmonics and the decrease in the nonlinear coefficient, with the progressing degradation, it is possible to appropriately determine the replacement cycle of SPDs before thermal runaway occurs.