Experimental Analysis of MCCB Interruption Behavior Under Repetitive Overcurrent Conditions for Electrical Safety in Low-Voltage Distribution Systems

A molded case circuit breaker (MCCB) is a key protective device for electrical safety in low-voltage distribution systems, and its interruption performance is closely related to arc behavior during fault-current interruption. This study experimentally analyzed variations in the interruption behavior of MCCBs under repetitive overcurrent conditions with different current magnitudes. In this study, new repetitive interruption experiments were performed under the 7 kA condition, while the 2.8 kA results reported in our previous study were used for comparison. Four MCCB products with the same model and rated specifications are prepared and denoted as Products A–D. Repetitive interruption tests are performed under the same procedure, and the voltage waveform generated during interruption is divided into the total arcing time, arc extension period, and energy consumption period. The time and energy distributions of each period are then quantitatively compared. The results showed that, from the first to the third test, the average total arcing time increased by approximately 4.68%, while e the arc extension time and arc extension voltage-area-based index increased by approximately 15.98% and 19.47%, respectively. In contrast, the energy consumption time and energy consumption voltage-area-based index decreased by approximately 5.90% and 12.87%, respectively. Although the difference between the first and second tests is relatively large, the changes between the second and third tests are small, with the total arcing time and total arcing voltage-area-based index changing by only approximately −0.57% and −0.30%, respectively. These results indicate that variations in MCCB interruption behavior under repetitive overcurrent conditions are more sensitively reflected in the time and energy distribution between the arc extension and energy consumption periods than in the total arcing time alone. Therefore, voltage-waveform-based analysis of interrupting time and energy consumption ratio can be used to evaluate interruption behavior variations and potential performance degradation of MCCBs, supporting reliability assessment for electrical safety under repetitive fault conditions.