Failure Analysis And Cross Section Shape Optimization Of High Voltage Circuit Breaker Energy Storage Spring

Recently,some of the same cases have happened that circuit breakers failed to work due to stress relaxation which was caused by energy-stored springs.The high-voltage circuit breaker energy-stored spring is an important component of the high-voltage circuit breaker,and its potential safety hazard seriously threatens the operation of the substation.China’s power industry is also moving toward high-pressure UHV.The safety of circuit breaker energy-stored spring has also been placed higher.On the one hand,after being tempered at different temperatures,the stress-relaxed 60Si2CrVA energy-stored springs and good-performed ones were investigated by the chemical composition analysis,tensile test,fracture analysis and metallographic analysis.Thus,we can use the study results to guide the production of 60Si2CrVA to improve the quality of the circuit breaker energy-stored spring.The results show that the tempering temperature of the spring was too high,leading to the formation of tempered sorbite&massive free ferrite.Besides,the thickness of the carbide was not uniform,and the coarse carbides in some regions reached a diameter of 0.5 μm,which decreased the obstruction of well-dispersed second-phase particles to the movement of the dislocations,so that the activation energy required for the stress relaxation of the material was reduced,and the stress relaxation rate of the spring was accelerated.On the other hand,in this study,the static stress analysis of cylindrical springs with different cross sections was performed by Solidworks Simulation,a finite element analysis software.The position of the maximum stress cross-section of the spring was determined by tools such as software-provided probes and cross-section trimming ISO cuts,and the stress values of the contour and different linear directions were detected on the cross-section.Besides,with the matlab data processing probe,we can analyze the influence of different spring cross-sections on the cylindrical coil spring’s stress distribution uniformity.The results show that,with the other parameters of the spring unchanged,the stress distribution on the cylindrical spiral spring with rectangular section was the most uneven,and the stress distribution on the cylindrical spiral spring with oval section was the most uniform.In the case of the same material and in the same application scenario,the design with an oval cross-section has a higher spring safety factor than the conventional circular cross-section.