Rated voltage: It means normal working voltage that circuit breaker withstands. The rated voltage refers to the line voltage. According to the regulations of the state, the rated voltage classes are: 10 kV, 35 kV, 60 kV, 110 kV, 220 kV, 330 kV and 500 kV. 

The highest working voltage: In consideration of that the transmission line has voltage drop and the rated voltage of busbar at power supply end is higher than the rated voltage of busbar of the power receiving end, in this way the circuit breaker may operate for a long time under the voltage higher than the rated voltage, therefore the maximum working voltage is specified for the circuit breaker. According to the national standard, for the equipment with rated voltage of 220 kV or under, its maximum working voltage is 1.15 times of rated voltage. For equipment of 330kV, its working provision is 1.1 times of rated voltage. 

Rated current: It refers to the working current shown on the nameplate that the circuit breaker can go through for a long time. 

Rated breaking current: Under the rated voltage, the maximum current that the circuit beaker can reliably turn off is called rated breaking current, showing the breaking capacity of the circuit breaker. 

Switching-on time: As for the circuit breaker with operating mechanism, the time required from sending the signal of switching-on (i.e. the closing coil is energized ) to switching on the circuit breaker is called the switching-on time. Generally the switching-on time is  greater than the switching-off time. 

Switching-off time It means the total time required from sending the signsl of tripping( the tripping coils are energized) to switching off the circuit breaker until the three-phase electric arc is completly extinguished. Generally the switching off time is between 0.03 seconds to 0.12 seconds.