APERIODIC CURRENT COMPONENT AND ARC EXTINCTION IN SF₆ CIRCUIT BREAKERS UNDER RESONANCE CONDITIONS IN RENEWABLE-RICH GRIDS

Abstract

Renewable energy integration increases operating variability and tightens voltage and reactive-power control requirements, which elevates the importance of reliable reactive-power management and robust switching practices in transmission networks. In this paper, renewable integration is treated as an operational context motivating the study; however, statistical or time-series quantification of switching-event frequency under different RES penetration levels is beyond the scope due to a lack of operational datasets. A case study of SF₆ circuit breaker damage during switching of a compensated overhead line with shunt reactors is presented. Mathematical models of the line and switching conditions are developed to analyze electromagnetic transients leading to a pronounced aperiodic (DC-offset) current component. It is shown that, under near-resonant conditions, the DC offset can dominate the steady-state component and cause a prolonged delay of the first current zero crossing (“no-zero” condition), thereby degrading arc-extinction conditions and potentially damaging the interrupter chamber. A physical interpretation of DC-offset formation is provided using operational calculus. The modelling results are validated using full-scale electromagnetic transient recordings of compensated-line switching events captured by substation monitoring systems; this validation confirms the fidelity of the transient mechanism and does not require renewable generation to be connected to the specific line used for validation. The findings support improved controlled-switching coordination and damping measures (including pre-insertion resistors and shunt-reactor switching strategies) for SF₆ circuit breakers under renewable-rich operating conditions.