Vacuum circuit breakers, like other types of circuit breakers, are inevitably subjected to the test of electricity, heat, machinery, atmosphere and time during operation. Therefore, the vacuum circuit breaker should meet the following requirements:

(1) The insulation is safe and reliable. Vacuum circuit breakers have to encounter the influence of operating voltage and atmospheric overvoltage during operation. Under the action of these overvoltages, their insulation will not be damaged and cause accidents.

(2) It can work for a long time under normal load and has a certain overload capacity. The heating of the vacuum circuit breaker mainly includes the heating effect of the conductive circuit and the contact resistance under the action of the load current and the thermal effect of breaking the short-circuit current. It should have good heat dissipation conditions and sufficient heat capacity to avoid damage due to excessive temperature rise.

(3) Sufficient mechanical strength. During the service life of the vacuum circuit breaker, it should be able to withstand the following external mechanical forces without damage during operation:

• Impact force of normal opening and closing;
• Electric power for breaking short-circuit current;
• Various internal stresses of the operating mechanism;
• The effects of earthquakes and other external forces.

(4) Limit cutoff value and reignition rate. Avoid damage to vacuum circuit breakers and other high-voltage electrical equipment due to overvoltage.

(5) Sufficient life span. Including vacuum life, mechanical life and electrical life.

(6) Simple structure, low cost, reliable working performance, convenient use and maintenance.