What are the main technical parameters of high-voltage circuit breakers? What does each represent?

1. Rated voltage
The normal operating voltage that a Circuit Breaker can withstand during operation. The maximum operating voltage refers to the highest voltage during the operation of the system where the circuit breaker is located. The maximum working voltage is 1.10-1.15 times the rated voltage.

2. Rated frequency
The normal operating frequency of the power grid connected to the circuit breaker is generally 50Hz in China.

3. Rated current
The effective value of the continuous current passing through a circuit breaker for a long time under specified usage and performance conditions (including ambient temperature). When passing through the rated current for a long time, the heating of each part of the conductive circuit of the circuit breaker shall not exceed the specified temperature rise.

4. The relevant parameters of circuit breakers and their ability to break short-circuit currents are as follows.

4.1. Rated short-circuit breaking current
Abbreviated as rated short-circuit current, it refers to the maximum short-circuit current that a circuit breaker can ensure normal breaking under the specified usage and performance conditions (including recovery voltage, non periodic components, short-circuit power factor, etc.). Usually, it is characterized by the effective value of the AC component and the percentage of the DC component of the warm current separated by contacts. The circuit with such current has a power frequency recovery voltage equal to the rated voltage of the circuit breaker and a transient recovery voltage equal to the standard specified value.

4.2. Rated short-time withstand current (rated thermal stability current).
The effective value of the short-circuit current that the circuit breaker equipment can carry in the closed state within the specified rated short-circuit duration under specified usage and performance conditions. The heating of each part of the circuit breaker shall not exceed the allowable value. Usually, the rated short-time withstand current of a circuit breaker is equal to its rated short-circuit breaking current.

4.3. Rated short-circuit duration.
The time interval of the rated short-time withstand current that the circuit breaker equipment can carry in the closed state. The rated short-circuit duration of 550-800kV circuit breaker equipment is 2s; the rated short-circuit duration of 252-363kV circuit breaker equipment is 3s.

4.4. Rated dynamic stability current (rated peak withstand current).
Under the specified usage and performance conditions, the peak current of the first half wave of the rated short-time withstand current that the circuit breaker equipment can carry in the closed state should not cause damage to the circuit breaker due to the electric force generated. The rated peak withstand current should be equal to 2.5 times the rated short-time withstand current and equal to the rated short-circuit closing current (peak value).

4.5. Rated short-circuit closing current.
Under the specified usage and performance conditions, the peak value of the first half wave of the current flowing through one pole of the circuit breaker during the manic state process after the current appears during the closing operation of the circuit breaker. The rated short-circuit closing current of a circuit breaker corresponds to the rated voltage and rated frequency. For a system with a rated frequency of 50Hz and a time constant standard value of r=45ms, the rated short-circuit closing current is equal to 2.5 times the effective value of the AC component of the rated short-circuit breaking current.

In addition, there are rated out of step breaking current, rated line charging breaking current, rated cable charging breaking current, rated capacitor bank breaking current, rated capacitor bank closing inrush current, rated small inductive breaking current, etc.

5. Time parameter of high-voltage circuit breaker.

5.1. Closing time refers to the time interval from the moment the closing circuit receives the closing command to the moment when the last pole arc contact contacts, abbreviated as fixed closing time.

5.2. The interval time refers to the time interval from receiving the disconnection instruction to the moment when all the arc contacts of the poles are separated. Abbreviated as fixed separation time.

5.3. The fully open and close time refers to the time interval from the moment the circuit breaker receives the opening command to the final extinguishing of each pole arc. In fact, the fully open and close time is equal to the sum of the circuit breaker's opening time and arc time.

6. Operation sequence during operation

The operation sequence refers to a series of specified operations at specified time intervals. The rated operation sequence of circuit breakers is usually divided into the following two types:

6.1. Automatic reclosing operation sequence
Instant separation - combined separation (CO) - t - combined separation; In this sequence, 0 is the no current time (referring to the time interval from the final extinguishing of the arc in all poles of the circuit breaker to the first current passing through any pole when it is subsequently reconnected), with a value of 0.3s or 0.5s; t is 180s (sometimes referred to as the forced transmission time); (i.e. 0-0.3s - C0-180s - CO).

6.2. Non automatic reclosing operation sequence
Namely, it is divided into t-CO-t-CO (or CO-t-CO). The closing and opening time (referred to as metal short-circuit time) is the time interval from the moment when the first phase contact contacts during the closing operation to the moment when all phase arc contacts separate during the subsequent interval operation. This sequence usually takes 15 seconds. If necessary, the circuit breaker can be marked with the corresponding breaking capacity under different operating sequences.

6.3. Regarding the integration of time, the following three points should be mainly explained:

When the opening and closing time of the circuit breaker is prolonged, it has an adverse effect on the stability of the system; When the closing time is too short and not conducive to the reclosing of the circuit breaker, the reliable breaking ability of the second "opening" is compromised. Therefore, there should be a range for the opening and closing time of the circuit breaker, and the manufacturer should provide the upper and lower limits of the opening and closing time of the circuit breaker, and verify the rated short-circuit breaking capacity of the circuit breaker at the specified minimum opening and closing time in the type test.