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Selection Principle Of Low Voltage Circuit Breaker
Aug 03, 2017

  Selection principle of low voltage circuit breaker

  1) Determine the type and protection of the circuit breaker according to the requirements of the line protection. - Determine the choice of frame type, device type or current limit type.

  2) The rated voltage UN of the circuit breaker shall be equal to or greater than the rated voltage of the protected circuit.

  3) Breaker undervoltage release The rated voltage shall be equal to the rated voltage of the protected circuit.

  4) The rated current of the circuit breaker and the rated current of the overcurrent release shall be greater than or equal to the calculated current of the protected circuit.

  5) The limit breaking capacity of the circuit breaker should be greater than the effective short circuit current of the line.

  6) The protection characteristics of the upper and lower circuit breakers in the distribution line should be coordinated and the protection characteristics of the lower level should be located below the upper protection characteristic and not intersect.

  7) The long delay trip current of the circuit breaker should be less than the permissible continuous current of the wire.

  (1) device type circuit breaker device type circuit breaker with insulated plastic shell, built-in contact system, interrupter and release, etc., can be manual or electric (for large capacity circuit breaker) closing. Has a higher breaking capacity and dynamic stability, a more selective protection function, widely used in distribution lines. Currently used DZl5, DZ20, DZXl9 and C45N (now has been upgraded to C65N) and other products. The C45N (C65N) circuit breaker has the advantages of small volume, high breaking ability, good current limiting performance, light operation, complete model specification and convenient combination on the basis of unipolar structure into two-pole, three-pole and four-pole circuit breakers , Widely used in 60A and below the civilian lighting branch and branch (more for residential users into the line switch and shopping street lighting switch).

  (2) frame type low-voltage circuit breaker frame type circuit breaker general capacity is larger, has a high short-circuit breaking capacity and high dynamic stability. Suitable for AC 50Hz, rated current 380V distribution network as the main protection of the trunk line. Frame-type circuit breakers mainly by the contact system, operating mechanism, over-current release, shunt release and undervoltage release, accessories and frames and other components, all components installed in the frame after the insulation structure. At present, China has commonly used DWl5, ME, AE, AH series of frame-type low-voltage circuit breakers. DWl5 series circuit breakers are developed and produced in China, the whole series with 1000,1500,2500 and 4000A and several other models. ME, AE, AH series of circuit breakers are produced using the introduction of technology. They are more complete specifications (ME switching current rating from 630A ~ 5000A a total of 13 levels), rated breaking capacity stronger than DWl5, commonly used in low-voltage power distribution main protection.

  (3) intelligent circuit breaker At present, the domestic production of intelligent circuit breaker frame and plastic shell type two. Frame-type intelligent circuit breakers are mainly used for intelligent automatic distribution system in the main circuit breaker, plastic shell intelligent circuit breaker is mainly used in the distribution network to allocate electricity and as a line and power equipment control and protection, but also Used as a three-phase cage asynchronous motor control. Intelligent circuit breaker is characterized by the use of a microprocessor or microcontroller as the core of the intelligent controller (intelligent release), it not only has a variety of common circuit breaker protection, but also with real-time display circuit in a variety of Electrical parameters (current, voltage, power, power factor, etc.), on-line monitoring of the circuit, self-regulation, measurement, test, self-diagnosis, communication and other functions, to a variety of protection functions of the operating parameters display, Modify, protect the circuit when the fault parameters can be stored in non-volatile memory for inquiries.