Basic characteristic parameters of circuit breaker

1) Rated working voltage UE

The rated operating voltage is the nominal voltage of the circuit breaker, which can be operated continuously under the specified normal service and performance conditions.

China stipulates that in the voltage grade of 220kV and below, 1.15 times of the rated voltage of the system is the highest working voltage; The maximum operating voltage for 330kV and above is 1.1 times of the rated voltage. The circuit breaker can maintain insulation under the highest operating voltage of the system, and can be closed and opened in accordance with the specified conditions.

2) Rated current In

The rated current is the current that the trip can pass for a long time under the ambient temperature of 40℃. For circuit breakers with adjustable trip, is the maximum current that the trip can pass through for a long time. When used in the ambient temperature over 40℃, but not higher than 60℃, allowed to reduce the load for long-term work.

3) Overload tripper current setting value IR

When the current exceeds the tripping current setting value, IR, the circuit breaker delays tripping. It also indicates the maximum current the circuit breaker can withstand without tripping. This value must be greater than the maximum load current Ib, but less than the maximum allowable current Iz on the line.

Thermal burst relay IR can be adjusted In the range of 0.7 to 1.0In, but with electronic equipment, the adjustment range can be much larger, usually 0.4 to 1.0In. For circuit breakers equipped with non-adjustable overcurrent slip relays, Ir=In.

4) Short-circuit trip current setting value IM

A short circuit trip relay (instantaneous or short delay) is used to trip the circuit breaker at a high fault current value with a tripping threshold of IM.

5) Rated short time tolerance current ICW

The value of current that is allowed to pass at a given time. The current value passes through the conductor at the appointed time without causing damage to the conductor due to overheating.

6) breaking ability

The breaking capacity of a circuit breaker refers to the ability of the circuit breaker to safely cut off the fault current. There is no necessary connection with the rated current. The former specifications are 36kA, 50kA, etc. It is generally divided into ICU of limit short circuit breaking capacity and ICS of operation short circuit breaking capacity.