Research On Action Characteristics Of AC Current Electromagnetic Trip System With Two Trip Values

The emergence and development of Smart Grid provides a new solution for the stable operation of power supply and distribution system.In the current terminal power distribution system,the three-stage fully selective protection of the miniature circuit breaker can be realized through the zone selective interlocking technology ZSI（Zone Selective Interlocking）.However,the current traditional electromagnetic release has only one trip value,which can only realize instantaneous protection,and does not have the short-circuit short-time delay protection function required by ZSI technology.Therefore,on the basis of the traditional electromagnetic release structure,this thesis adds a secondary short-circuit winding,making it a new structure of an AC current electromagnetic release with two tripping values.The new electromagnetic release can realize short-circuit short-time delay protection and short-circuit transient protection.This topic comes from the National Natural Science Foundation of China Project "Research on New Thermo-electromagnetic Hybrid Intelligent Miniature Circuit Breakers and Intelligent Low-Voltage Distribution Microsystem"（51777129）.The main work of this thesis is as follows:Firstly,in order to study the design method of the double trip value electromagnetic release at different trip values,the main factors affecting the field weakening performance of the short-circuit winding and the magnitude of the trip current are analyzed.The main influencing factors are deduced by the magnetic circuit analysis method,and the simulation model and dynamic simulation model of the influencing factors of the field weakening performance of the dual-winding electromagnetic trip system based on Simulink are established,and the change law of the main magnetic flux and electromagnetic attraction force before and after the secondary winding is short-circuited is analyzed.The simulation results also show the effectiveness of the field weakening method.Secondly,according to the simulation results and the instantaneous trip current range of the electromagnetic release,the design requirements and basis of the electromagnetic release with double trip value are put forward;The electromagnetic suction force at the open position is taken as the precondition,and the structure design and related parameter calculation are carried out for the electromagnetic system of the double trip value electromagnetic release.Thirdly,in order to verify whether the designed electromagnetic release can operate reliably under the set excitation current,the static characteristic analysis is carried out by using Maxwell electromagnetic analysis software,and the magnetic field intensity distribution diagrams under different air gaps and different short circuits are obtained.The static suction curve under current shows that the electromagnetic release meets the design initial conditions.Finally,the dynamic simulation model of the double trip value electromagnetic trip unit is established,and the Maxwell electromagnetic analysis software and the ADAMS virtual prototype technology are used for co-simulation to discuss the action characteristics of the double trip value AC electromagnetic trip system.The dynamic results show that the electromagnetic tripping The system can trip under the rated set current,which has the prerequisites for realizing selective protection and meets the design requirements.