Failure Mechanism of Oil-immersed Louver Contacts in the UHV Converter Valve
Oil-immersed louver contacts,as a key current-carrying connection component for the lead-out wire and bushing in the elevated seat area of the ultra-high voltage converter valve,plays a crucial role.The overheat failure of the louver contacts on the valve side,leading to excessive direct resistance,constitutes a serious safety hazard in the power system.Based on the degradation distribution characteristics of the louver contacts,this paper clarifies the external causes that trigger its overheat failure.Through scanning electron microscopy,energy-dispersive X-ray spectroscopy,X-ray dif-fraction,inductively coupled plasma,and simulated experiments,the degradation failure mechanism of the oil-immersed louver contacts is explored.The results indicate that uneven pressure on the louver contacts caused by misalignment leads to overcurrent in some finger segments of louver contacts,resulting in local high temperature.Under high-temperature conditions,silver-plated copper finger segments undergo pitting corrosion,and the copper substrate forms a silver-copper primary cell with the silver plating and insulating oil,generating corrosive silver-sulfide-oil and copper-sulfide-oil com-pounds,as well as copper-silver sulfide and cuprous sulfide.This process leads to the destruction of the silver plating,reduced adhesion,and increased contact resistance of the finger segments.Wear in the electrical contact area and plastic deformation of the stainless-steel framework at high temperatures further accelerate the degradation of the louver contacts.The research conclusions can serve as a reference for the design,fault analysis,and further study of oil-immersed electri-cal contact components.
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维普
