The Research Of Miniature Circuit Breaker With Short Circuit Protection For Zone Selective Interlocking

With the development and construction of the smart grid,power distribution system in the protection of the selectivity and rapidity have attracted more and more attention,but the traditional current setting and time setting have their inevitable disadvantages.The technology of zone selective interlocking has the advantages of current setting and time setting,which can take into account both the selectivity and rapidity of protection.However,all of the circuit breakers are required to have a certain intelligent function.In addition to the lowest level of the circuit breaker,other levels of circuit breakers need to have three stages of protection.Unfortunately,the application of the zone selective interlocking technology in the power distribution terminal system is limited,the reason is that the miniature circuit breaker does not have t short delay protection function.According to the working principle of AC electromagnet short circuit,a new theory is proposed,which can realize the function of short circuit short delay.In the excitation magnetic potential is constant,changes the main magnetic flux in the magnetic circuit can be controlled through the double winding coil is switched on or switched off,which can change the electromagnetic force,control the working state of the miniature circuit breaker,so as to achieve the purpose of short time delay.First of all,according to the structure and motion characteristics of miniature circuit breaker,the working principle of zone selective interlocking technology,the paper puts forward the overall plan of double winding controllable electromagnetic tripping device with short circuit protection.Then,through the Maxwell equation theory,the main influencing factors of the minimum tripping current double winding controllable electromagnetic tripping device are analyzed under the two different working conditions.The mathematical model of double winding controllable electromagnetic tripping device are established based on the Simulink module of MATLAB software.And the main factors are further analyzed by magnetic circuit simulation.The simulation results are consistent with theoretical analysis,verify the feasibility of double winding theory.Then,with the DZ47-60 miniature circuit breaker for reference,a new type of circuit breaker electromagnet is designed by setting the working air gap,the spring reaction force and the electromagnetic force of the key points.Finally,the 3D magnetic field model of miniature circuit breaker double winding electromagnetic tripping device is established by Ansoft software.Then the structure of the double winding controllable electromagnetic tripping device is optimized.The double winding controllable electromagnetic tripping device,realizing short-circuit short delay protection for the miniature circuit breaker,not only for the zone selective interlocking technology has laid a solid foundation in the use of the distribution terminal,but also the selective protection for distribution system may be provided.