As the main product of terminal electrical appliances, the development of miniature circuit breakers has always led the development of terminal electrical appliances. Selective protection of terminal distribution system has not been realized in the past. The birth of miniature circuit breakers with selective protection, such as ABB S700, has completely solved the selective protection of upper and lower levels of terminal distribution system, and greatly improved the safety and reliability of using electricity. In recent years, micro-circuit breakers with P+N structure have developed rapidly. At present, micro-circuit breakers with P+N structure are developing towards large capacity and high interrupting capacity. With the breakthrough of P+N structure and micro-circuit breaker technology, micro-circuit breakers with smaller size (predicted 12 mm unipolar width) will be available in the near future, which will usher in micro-circuit breakers. Another development peak. The same miniature circuit breaker has a variety of tripping characteristics, can meet a variety of standards, meet the requirements of different distribution systems, and meet the needs of global trade. In addition to its own technological development, miniature circuit breakers have more complete accessories. There are new breakthroughs in the installation of miniature circuit breakers. From screw installation to track installation, the installation of miniature circuit breakers is more convenient. At present, the integration technology of bus bar connection and installation is adopted by more and more miniature circuit breakers to improve production efficiency.