The selection of rated current value and rated short-circuit breaking current value should be based on the actual capacity of the power grid, and try to overcome the tendency of taking the larger the insurance factor as much as possible. If the value is too large, it is not cost-effective, and it will also affect the current performance. , resulting in the occurrence of cut-off overvoltage. The selection of rated current should be based on 2000A and below, and the selection of short-circuit current value should be based on "urban network planning and transformation, 10kV is 20kA, 35kV is 25kA, and the blind pursuit of excessive insurance factor is avoided.
Most of the operating ambient temperature of high-voltage vacuum circuit breakers is - 30°C ~ + 40°C. In actual use, when the ambient temperature is low, the friction of the circuit breaker transmission mechanism increases significantly. Under normal temperature conditions, the opening and closing operation force of the circuit breaker obviously cannot meet the friction requirements of the mechanism when the temperature is low, resulting in the failure of opening and closing. If the short-circuit fault current is opened or closed at this time, an abnormality will occur, and even an explosion will occur. Therefore, it is indicated in the product manual that the ambient temperature of use is at the site of special use environment.