The method for determining the rated parameters of low-voltage circuit breakers (automatic switches) is as follows:

1. The rated voltage should not be lower than the line rated voltage.
2. The rated current (including the rated current of the trip unit) should not be less than the calculated load current of the circuit.
3. The limit making and breaking capacity should be greater than (or equal to) the maximum short-circuit current in the controlled circuit.
4. The ratio of the single phase-to-ground short-circuit current at the end of the line to the set current of the instantaneous (or short-delay) release of the automatic switch should be greater than (or equal to) 1.25.
5. The rated voltage of the automatic switch under-voltage release should be equal to the rated voltage of the line.