Influence of circuit breaker mounting on its lifetime

The circuit breaker is one of the crucial elements of power grids and its failure might have severe or even fatal consequences for the grid or its operators. To prevent failure of this critical device, loading conditions must be thoroughly analysed. The load put on the device has two components, electrical and mechanical. This work is focused on the later one, which is caused by high speeds, accelerations and springs forces. Nowadays, these mechanical loads are increasing with the transformation of the grid. One of the influencing factors of circuit breaker endurance, which was not analysed yet, is the type of circuit breaker mounting. The question of this work is whether different types of circuit breaker fixation have a provable influence on the lifetime of circuit breaker. The simulation approach was chosen over physical test. Specifically, a finite element model of a medium voltage circuit breaker was employed. Stresses of selected parts were used to evaluate the influence on the lifetime. Different types of circuit breaker mounting with varied stiffnesses were investigated, namely stiff and soft foundation, test bench made of aluminium profiles, rack seat, and varied thicknesses of circuit breaker housings. Despite the slight variation in stress results of the selected actuator components, variations are deemed not significant enough with respect to the considerable variations in stiffness. Ultimately, it is concluded that the fixation of circuit breakers during mechanical endurance testing does not lead to significant variation in part strength and travel curves of the system. Moreover, it is suggested that inclusion of the housing in mechanical circuit breakers models may not be necessary.