Analysis of Interrupting Energy Variations in MCCBs Under Repetitive Fault Conditions in Accelerator Environments

This study quantitatively analyzed the effects of repetitive fault currents occurring in an accelerator environment on the breaking performance of molded-case circuit breakers (MCCBs). To this purpose, four MCCB samples are subjected to one, two, and three repeated fault tests. The interrupting process is divided into the arc stretch and moving (t1–t2) section and the absorption in the splitter plate (t2–t3) section, and the energy and time are analyzed. The experimental results show that the total energy consumption increased by an average of 1.8–1.9 times in the second and third tests compared to the first test, and the interruption time is also extended by 1.6–2.0 times. In particular, the energy increase rate in the t2–t3 section is the highest, at an average of 220%, indicating that the splitter plate is thermally saturated and significantly affected by hot gas due to repeated breaking. These results imply that the thermal and electrical performances of MCCBs deteriorates in a repetitive fault environment, with the interrupting speed delayed and internal energy loss increased. This study suggests the possibility of energy-based condition diagnosis using the energy consumption ratio of each section. Furthermore, the ratios can be used as basic data for evaluating the reliability of circuit breakers under repetitive failure conditions and building predictive maintenance models.