Design Of Phase-controlled Reclosing Circuit Breaker's Control Strategy And Operating Mechanism

Circuit breakers in power system have widely used reclosing technology to improve power supply reliability.However,when a permanent fault occurs in power system,circuit breakers will reclose to a permanent fault,resulting in a large reclosing current with a high energy.It willlead to a greater impact on the equipments on the transmission line,reducing power quality and affecting users.This thesis studies the control strategy of phase-selection reclosing and design of operating mechanism in response to this problem,which is of certain theoretical significance and engineering application value.This thesis proposes a tentative phase-selection reclosing operation method.By controlling the circuit breaker to close at the appropriate phase,and controlling the circuit breaker to complete the closing and opening actions in a short period of time,short-time closure is achieved to determine the state of the line.We builds a power system model based on the actual power system parameters,then simulates and analyzes the power system under transient and permanent fault conditions,to find out the electrical signal quantity that can determine whether transient fault or permanent fault,and to optimize closing time and opening time.Then,we perform the simulation analysis of the power system on the three situations that the transmission lines contain distributed loads,a disconnection fault occurs in power lines,and the transition resistance is too large.Finally,the designed control strategy is optimized to obtain the final new phase-controlled reclosing control strategy.This thesis designs a double monostable permanent magnet actuator and an eddy current repulsive force-driven permanent magnet actuator,and provides three command modes: closing,opening and short-term closure.Through the simulation,we analyze the static and dynamic characteristics of the two actuators in the three modes,and compare the advantages and disadvantages of the two permanent magnet actuators.The research results show that the new phase-seclection circuit breaker can not only reliably determine whether the fault is permanent,but also effectively reduce the impact of reclosing on the power system.Besides,the two new mechanisms designed can meet the short-term closure requirements of the proposed control strategy.