All protection is based on load, so, to understand the setting of overload protection value, according to the electrical design manual, you take the reliability coefficient between 1.15 and 1.25;

Instantaneous protection is determined according to the instantaneous maximum short circuit current at the moulded case circuit breaker's point. According to experience, the rated current of distribution type is 10 times, and that of motor protection type is 12 times. Note that the rated current is not setting current.

Short delay is better understood. It is proposed for class B circuit breakers. The specific time and current parameters should be set according to the setting value of the upper and lower moulded case circuit breakers and the expected short circuit current of the point. The short delay time should be no less than the following. The short delay time, the short delay current and the long delay reverse time of stage breaker are compared, and the fixed time and instantaneous protection value are compared.