Research Of Molded Case Circuit Breaker With Zone Selective Interlock

Distribution network is an important part of electric utilization, and is inseparable fromproduction and living. The circuit breaker is an essential protect and operate apparatus inthe distribution system, and its performance is related to the security of human life andproperty. With the improvement of the social productive forces, the concept of intelligentpower grids is gaining popularity, research on intelligent MCCB(Molded Case CircuitBreaker) is attracting more and more attention from industrial and academic field.Starting from the technological development and market demand, this thesis analyzesthe historical development of intelligent MCCB, and summarizes the technical status ofboth domestic and foreign related research, finds the clue of technical and functionaltrends, studies and designs an intelligent controller for MCCB with ZSI(Zone SelectiveInterlock).According to the application context of circuit breaker, the thesis proposes thefeatures for the intelligent circuit breaker controller, and divides the overall hardwareproject into power module, signal sampling circuit, interface module, networkcommunication interface. Specially, the power module combines self-produced powersupply and backup power. The hardware design and its control strategy of self-producedpower supply is discussed. Considering the practical requirements and technical trends,the thesis selects Ethernet to accomplish network communication.The thesis implements the controller software based on uC/OS real-time kernel.6tasks are created to achieve the functions of electrical parameter calculation, protection,human-machine interface, data storage, self-diagnoses, and network communication. theimplementation of these tasks is illustrated in detail, and the synchronization and mutualexclusion policy is shown.On the horizon of distribution system, the thesis studies selective protect ofovercurrent fault in the whole current range, analyzes the current selective, time selectiveand logic selective principles, summarizes their characteristics. According to the nationalstandard GB/T22710-2008, the thesis achieves the3-sectional protection by simulating thethermal effect of current. As a more advanced protect strategy, the principle of zoneselective interlock is elaborated, and a solution of ZSI through Ethernet is proposed.The test platform is built, the breaker controller is tested from self-produced power supply,3-sectional protection to zone selective interlock and Ethernet communication.Experiments show that the controller accomplishes all the above features and the accuracymeets the relevant requirements.