Research On Network Of Miniature Circuit Breaker Controllers For Full Range ZSI Protection

The intelligentization of distribution electrical appliances is an important part of smart grid construction.Among them,low-voltage miniature circuit breakers are the most widely used low-voltage power distribution appliances,and their output value accounts for more than 50% of the total output value of low-voltage electrical appliances.It is of great significance to study miniature circuit breakers,and to study the three-stage current protection of intelligent miniature circuit breakers and to optimize the existing ZSI area interlock protection is the most important.This topic comes from the National Natural Science Foundation of China: Key Issues in New Thermal Electromagnetic Hybrid Release and Networked Selective Protection of Circuit Breakers(Project No.51777129).The existing circuit breaker ZSI protection only contains the short-circuit section,which can not deal with the selective protection problem when multiple positions are overloaded or the lower-level circuit breaker overload protection fails.Therefore,a smart breaker controller network based on CAN bus is designed in this paper.This controller network differs from traditional smart breaker controller functions and adds a central controller.The circuit breaker controller is only responsible for the realization of the traditional three-stage current protection related electrical signal measurement calculation,human-computer interaction and electronic tripping.When it comes to ZSI protection,the fault information is sent to the central controller through the CAN bus.The central controller collects the fault conditions of the circuit breakers according to the needs,and based on the protection principle of the upper and lower levels of the circuit breaker,arbitrates the tripping treatment of each circuit breaker ZSI to realize the full range ZSI protection function of the line short circuit section and the overload section fault.First of all,according to the existing three-stage current protection technology,ZSI protection technology and the functional requirements of smart grids for intelligent circuit breakers in the future,Improve the network theory part of the intelligent circuit breaker controller designed in this paper,and build the short circuit and overload model of the low voltage distribution network,and analyze the current and voltage of the circuit breakers at various levels when the fault occurs.Secondly,completed the hardware design of the intelligent circuit breaker controllernetwork,including the basic system part of the STM32 single-chip microcomputer,the power module part,the human-computer interaction module part,the CAN hardware node module part,And the circuit breaker unit unique electrical signal acquisition conditioning conversion module part,analog trip module part.Then,based on the built-in hardware circuit,the main program of the circuit breaker controller and the central controller,the sampling A/D conversion program,and the human-computer interaction program are completed by the ?C/OS-II real-time operating system.In particular,it implements the three-stage current protection program,the short-circuit section and the overload section ZSI protection program associated with the implementation of the protection function and defines the arbitration of the priority between the sub-programs.And the CAN communication protocol is customized based on the functional requirements of the designed controller network.Finally,completed the construction of the physical platform,and checked the working conditions of the hardware circuit part and the software module part,including overload long delay protection,short circuit short delay inverse time limit protection,short circuit fixed delay protection,short circuit instantaneous protection and full range ZSI protection communication.And completed functional verification of the built controller network.