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(1) Rated voltage (nominal voltage): It is a parameter that characterizes the insulation strength of the circuit breaker. It is the standard voltage for long-term operation of the circuit breaker. In order to meet the requirements of power system work, circuit breakers also specify the maximum operating voltage corresponding to the rated voltage of each level. For 3-220KV levels, the maximum operating voltage is approximately 15% higher than the rated voltage; for 330KV and above, the maximum operating voltage is approximately 10% higher than the rated voltage. Circuit breakers should work reliably for a long time under the highest working voltage.
(2) Rated current: It is the parameter that characterizes the long-term current capability of the circuit breaker, ie, the maximum current that the circuit breaker allows for continuous long-term passage.
(3) Rated breaking current: It is a parameter that characterizes the breaker breaking capacity. Under the rated voltage, the maximum current that the circuit breaker can guarantee to break reliably is called the rated breaking current, and its unit is expressed by the kiloampere number of the effective value of the periodic component of the instantaneous short circuit current of the circuit breaker contact. When the circuit breaker operates in a grid below its rated voltage, its breaking current can increase. However, due to the limitation of the mechanical strength of the arc extinguishing chamber, the breaking current has a maximum value, which is referred to as the limiting breaking current.
(4) Dynamic stable current: It is the parameter that characterizes the short-circuit current capability of the circuit breaker and reflects the ability of the circuit breaker to withstand the electrodynamic effects of the short-circuit current. When the circuit breaker is in the closing state or closing moment, the maximum current that is allowed to pass through is called the electric stable current, which is also called the limiting passing current. When a circuit breaker passes through a stable current, it cannot be damaged by electrodynamic forces.
(5) Closing current: It is the parameter that characterizes the circuit breaker's closing current capability. Because the circuit breaker is closing the circuit, there may be a short-circuit fault in the circuit. At this time, the circuit breaker will close a large short-circuit current. In this way, on the one hand the electromotive force of the short-circuit current weakens the operating force of the closing, and on the other hand, an arc is generated as a result of the breakdown before the contact has been made, which may cause the contact to be welded, thus causing damage to the circuit breaker. The maximum peak current of a circuit breaker that can be reliably closed is called the rated closing current. The rated closing current and the dynamic steady current are equal in magnitude and both are equal to 2.55 times the rated breaking current.
(6) The duration of the thermal stabilization current and the thermal stabilization current: The stabilization current is also a parameter that characterizes the short-circuit current capability of the circuit breaker, but it reflects the ability of the circuit breaker to withstand the thermal effects of the short-circuit current. The thermal stability current is the maximum value of the periodic component of the current that is allowed to pass through the circuit breaker in the closing state for a certain duration. At this time, the circuit breaker should not be damaged due to short-term heating. According to national standards, the rated thermal stability current of a circuit breaker is equal to the rated breaking current. The rated thermal stable current duration is 2S. When it needs to be greater than 2S, 4S is recommended.
(7) Closing time and opening time: This is the parameter that characterizes the operating performance of the circuit breaker. Different types of circuit breakers have different time points for closing and closing, but they all require quick action. The closing time refers to the time from the closing of the closing coil of the circuit breaker operating mechanism to the touching of the main contact. The opening time of the circuit breaker includes the inherent opening time and the arc extinguishing time. The inherent opening time refers to the time from the opening of the opening coil of the operating mechanism to the separation of the contacts. The arc extinguishing time refers to the period from the separation of the contacts to the extinction of the arc of each phase. Therefore, the opening time is also referred to as the full opening time.
(8) Operating cycle: This is also an indicator of the operating performance of the circuit breaker. Short-circuit faults in overhead lines are mostly temporary. After the short-circuit current is cut off, the fault quickly disappears. Therefore, in order to improve the reliability of the power supply and the stability of the system operation, the circuit breaker should be able to withstand one or two more closing, breaking, or immediately opening and closing after closure. This kind of operation that divides and combines several times according to a certain time interval is called an operation cycle.
China's rated circuit breaker rated operating cycle is as follows:
Automatic reclosing operation cycle: minutes - t' - points - t - points non-automatic reclosing operation cycle: minutes - t - points - t - points in which, points - said Breaking action;
Combined points - indicates the action of closing the gate immediately after closing;
t'——No current interval time, that is, when the circuit breaker opens the fault circuit, the time from the arc extinguishing to the time when the circuit is automatically turned on. The standard time is 0.3S or 0.5S, that is, the reclosing action time.
t——For the operator to send power, the standard time is 180S
Outline of main technical parameters of high voltage circuit breaker
The following parameters are generally used to characterize the basic operating performance of high voltage circuit breakers: