Design And Analysis Of Fault Current Incentive Type Hybrid Circuit Breakers

With the rapid development of the smart grid construction, the demand for intelligent electrical equipment and the capacity of the grid is continuous growing. As the core equipment of closing and opening the grid load current and short-circuit current, the reliability and performance of circuit breaker have become increasingly important. With quick action speed and high reliability, the research of the repulsive force actuator circuit breaker based on the eddy current principle has gradually become one of the hottest topics in today's society.Based on the characters of quick repulsive force actuator, a kind of new type fault current energized fast circuit breaker was designed in this paper. With bus shunt as excitation current, dual coils in series repulsive force actuator and permanent magnetic actuator were composed together. This new type hybrid circuit breaker doesn't need receiving the order from logical judgment system and needless driven capacitor energy storage system either. With spontaneous rapidity, it can response fast and its actions are proportional directly related with the short current value.Some simulation analysis and optimization had been carried on based on this new structure. The paper established the mathematical model of the hybrid circuit breaker through theoretical analysis. In order to achieve opening fast repulsive force actuator with short-circuit fault current, the finite element model was established in Ansys Workbench. Then the coils' temperature-rise and turn-to-turn voltage of the new actuator under normal load were calculated to guarantee thermal stability and insulation reliability, and the effect of output repulsive force was also analyzed to ensure the action reliability. Combined with theoretical calculations, the study determined the structural parameters of the repulsive force actuator and simulated the electromagnetic fields of the repulsive force and permanent magnetic actuator with Ansys Maxwell. The simulation ensured the reliability and feasibility of the action under the designed parameters.With the consideration of short-circuit current broke in advance may lead to the loss of repulsion force during the actual opening process, failure issues may arise. The paper found out the most harsh opening situation by simulation, and analyzed the methods to avoid short-circuit current breaking by optimizing the current redundancy and opening spring initial force. The study also ensured that when the short-circuit current is too large to break in the first zero crossing, the circuit breaker can finish the opening process successfully by the moving part inertia and opening spring. Finally, the action mechanism of the new self-excitation hybrid circuit breaker was also discussed in this paper. For when the short-circuit current can't reach the threshold or the overload protection was required, this article applied the method of auxiliary permanent magnet actuator to assist opening. When the system needs circuit breakers, permanent magnet actuator following acts each time.Based on finite element analysis and simulation of the actuator, the fault current incentive type hybrid circuit breaker prototype was manufactured, and the correctness and reliability of simulation results were verified by experiments. The experimental data verified that the new actuator can break circuit quickly and successfully under the presetting short-circuit threshold of 2.4kA. The analysis and experiments provided a comparative complete exploratory research of this new type of incentive mode circuit breaker, also a good basis and reference for further research and application design.