Optimization of Shaft Sleeve Slippage in High-Voltage Circuit BreakerOperation Mechanism

High-voltage circuit breakers are mechanical switching devices which connect and break current circuits (operating currents and fault currents) and carry the nominal current in closed position. As a result of multi-running, the shaft sleeve in operation mechanism could slip and even strip from the shaft at the hinge joint, which decreases the system reliability. In this work, investigations on the cause of sleeve slippage are proceeded, and the dimension parameters of shafting components where sleeve slippage occurs are optimized by incorporating a quasi-static mechanical model with Taguchi method. By developing and analyzing the mechanical model for the shaft sleeve slippage, it indicates that the sleeve slippage displacement has a same variation tendency with the shaft deflection. Theoretical equations are derived by using force analysis and superposition method to descript the analytic function of the shaft deflection. As the variables within the analytic function of the shaft deflection, the diameter and length of the shaft and the corresponding shaft sleeve length are selected as the control parameters in the optimization model. Moreover, several experiments are conducted by using the L18 (mixed orthogonal array) design method. Considering that the local mechanical characteristics such as sleeve strain are difficult to monitor via experimental method, an FEM simulation model is established to give the sleeve slippage displacement. Different levels of control parameters are introduced into the mechanical model and FEM simulation according to Taguchi method. The results from signal-to-noise (S/N) and ANOVA analysis (analysis of variance) reveal that shaft diameter is the most significant factor determining sleeve slippage in high-voltage circuit breaker operation mechanism, and that a larger diameter of shaft, a shorter shaft length and a longer sleeve length can reduce the sleeve slippage effectively. Meanwhile, the theoretical model is verified and enhanced by the FEM model.