Basic requirements and principles of circuit breaker selection

Promulgator : TAIXIDate : 2018-08-31Views : 374

The main role of circuit breakers is to protect electrical appliances and isolate line load, in general, to meet the following basic requirements:

1) The selection of household circuit breaker to meet the line load characteristics. When choosing a circuit breaker, first of all, it is necessary to know its performance accurately, so as to set the parameters of the electrical appliances. Specific standards should conform to the "Low Voltage Distribution Design Specification";
2) Choosing a suitable circuit breaker should take into account the factors of AC, frequency, DC, voltage, etc., and the rated voltage and rating of the circuit. Frequency as the basis for selection;
3) Determine the load current value, and to determine the setting current of low-voltage circuit breakers;
4) Selecting the appropriate household circuit breaker needs to consider the surrounding environmental factors, such as ambient temperature, humidity and terrain altitude, in addition to considering the environmental pollution level and bear the impact of the environment.
5) According to the accurate parameters of short circuit, the breaking capacity, dynamic stability and thermal stability of the circuit breaker should be determined;
6) According to the selective protection requirements of the system, the matching of the upper and lower circuit breakers should be determined. The main principles of low voltage circuit breaker selection are:
1) The selection of household circuit breaker to meet the basic requirements of the load nature of the circuit breaker itself and the type of fault;
2) The rated voltage and frequency of the 6ka circuit breaker to be compatible with the nominal voltage and frequency of its circuit. In addition, the rated current of the low-voltage circuit breaker should be higher than the calculated current of the circuit in which it is operating normally;
3) When choosing a suitable low-voltage circuit breaker, the surrounding environment should be fully considered;
4) Under short-circuit conditions, the low-voltage circuit breaker should be able to meet the basic requirements of dynamic stability and thermal stability. Requirement. To ensure the normal operation of low-voltage distribution system, we must first be able to meet the selective action between the upper and lower levels of the circuit breaker. In practice, the higher level of circuit breakers will choose to use selective circuit breakers, while the lower level of 6ka circuit breaker will choose to use non-selective circuit breakers, such a choice can use the delay action to obtain selectivity.
A switchgear capable of switching on, carrying, and interrupting current under normal circuit conditions, and of switching on, carrying and interrupting current under abnormal circuit conditions within a specified period of time. Circuit breakers are generally made up of contact system, arc extinguishing system, operation mechanism, release, shell and so on. Circuit breakers are divided into high-voltage circuit breakers and low-voltage circuit breakers according to their scope of use. The dividing line between high and low voltage is blurred. Generally, circuit breakers above 3KV are called high-voltage electrical appliances.

The working principle of circuit breaker is:
The principle of 6ka circuit breaker is that when short circuit occurs, the magnetic field generated by large current overcomes the reaction spring, the release pulls the operation mechanism, and the switch trips instantaneously. When the overload occurs, the electrorheological (ER) becomes larger, the calorific value increases, and the bimetal sheet deforms to a certain extent to promote the action of the mechanism. The larger the current, the shorter the action time. Circuit breaker has electronic type, use transformer to collect the magnitude of each phase current, compared with the set value, when the current is abnormal, the microprocessor sends out a signal, so that the electronic release to drive the operation mechanism.