The breaking capacity of circuit breaker is not the greater the better, it can be said that it is suitable for electronic circuit breaker with adjustable protection value or circuit breaker with intelligent controller, but it is not suitable for thermal magnetic circuit breaker. So dada electric take you to understand the breaking capacity of the circuit breaker is what happened? What are the parameters that affect the safe operation of circuit breakers?
Main performance parameters of circuit breaker: rated voltage Ue, rated insulation voltage Ui, rated impact withstand voltage Uimp, rated current In, rated short-circuit on capacity Icm, rated limit short-circuit break capacity Icu, rated short-circuit break capacity Ics, rated short-circuit withstand current Icw.
The function of the circuit breaker is to connect, load and break the normal current, the most important is to be able to connect, load and break the fault current in the abnormal state (overload, short circuit). In fact, connecting normal current and abnormal current is not the most important performance of the circuit breaker, and the breaking fault current is an important indicator to judge the merits of the circuit breaker.
The breaking capacity of a circuit breaker refers to the ability of the circuit breaker to disconnect the fault current and isolate the fault area within a specified period of time when a short circuit or other large current impact occurs, so as to protect the safety of the device and prevent the further expansion of the accident.
There are two indicators of breaking capacity. According to the provisions of “GB 14048.2-2008 Low-voltage switchgear and control Equipment — Part 2 circuit breakers”, we simply summarize their differences:
(1) Rated operating short-circuit breaking capacity Ics: rated operating short-circuit current that can be broken by the manufacturer according to the conditions specified under the corresponding rated voltage. Is the circuit breaker can cut off the short circuit current, the circuit breaker can still be used normally.
2. Rated limit short-circuit breaking capacity Ics: the limit short-circuit current that can be broken by the manufacturer according to the specified conditions under the corresponding rated voltage. Is the circuit breaker can break off the short circuit current, can only bear a split, can not be used again.
Usually the rated limit of domestic circuit breaker short circuit breaking capacity than the rated operating short circuit breaking capacity to be large, and the joint venture or imported circuit breaker two values are equal.
Sometimes we will have some mistakes, blindly pursuit of high section of the circuit breaker is not appropriate. Because the power system has protection coordination from bottom to top, the protection fixed value is also selective.
A circuit breaker with adjustable constant value is of course the larger the breaking capacity the better, because his protection constant value can be adjusted according to the load.
But now the most used on the market is the fixed value of unadjustable thermal magnetic circuit breaker, circuit breaker as a protective element to be equipped according to the following electric equipment current and nature. General short-circuit current is 10 times the rated current, if the breaking capacity is greater, and cannot be adjusted, it can only make the following fault more and more enlarged, and even if the coordination is not good, there will be leap-step trip.
Post time: Mar-24-2022