The tripping mechanism of the switch is a set of connecting rod devices. When the main contact is closed through the operating mechanism, it will be locked in the closing position by the locking hook. If there is a fault in the circuit, the relevant release will act to release the locking hook in the release mechanism, and the main contact will quickly break under the action of the release spring. According to the different protection functions, the release can be divided into over-current release and voltage-loss release.