The BKM3EL series IoT-type residual current circuit breaker is suitable for three-phase four-wire low-voltage power grid systems with a directly grounded neutral point, operating at 50Hz AC, rated insulation voltage of 1000V, and rated operating voltage up to 400V. This series of circuit breakers features overload protection, short-circuit protection, residual current protection, overvoltage protection, undervoltage protection, phase loss protection, and reclosing functions. It can also prevent electrical fires and equipment damage caused by grounding faults in electrical lines or equipment, and provide indirect contact protection against electric shock hazards. This series of circuit breakers conforms to the following standards: IEC 60947-1 and GB/T 14048.1 "Low-voltage switchgear and controlgear - Part 1: General"; IEC 60947-2 and GB/T 14048.2 "Low-voltage switchgear and controlgear - Part 2: Circuit breakers"; and IEC 60947-4 and GB/T 14048.4 "Low-voltage sw