Abstract
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.
Highlights
High-voltage circuit breaker prevents system from severe damage due to overload, and so far, has been among the most important equipment for ensuring the effective and safe operation for the electric power system [1]
A significant jump of shaft deflection amplitude appears between the test nine and ten as a result of shaft diameter decreasing from the test nine to ten
According to the results evaluated by using S/N ratios and analysis of variance (ANOVA) method, the following conclusions are drawn: 1. According to the verification of confidence interval and the results comparison between mechanical model and finite-element model (FEM) simulation, the results from mechanical model are in close agreement with the FEM simulation results
Summary
High-voltage circuit breaker prevents system from severe damage due to overload, and so far, has been among the most important equipment for ensuring the effective and safe operation for the electric power system [1]. With a higher requirement in power load and mechanical response speed in industrial application, the reliability of the highvoltage circuit breaker operation mechanism is hard to be ensured due to its high working pressure and complex working condition. Lots of accidents appear in circuit breaker operation mechanism as a result of shaft sleeve slippage and falling. Feng et al [4] investigated the movement characteristics of circuit breaker closing and opening. His results indicated that the shaft sleeve slippage caused the condition due to which the
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