Mechanical Modeling of Oil-Immersed Louver Contacts on the Valve Side of a Converter Transformer

Degradation of the mechanical properties of oil-immersed louver contacts is an important cause of exceeding the DC resistance on the valve side of extra-high voltage converter transformers. In this paper, the mapping relationship between force-deformation and force-contact resistance of oil-immersed louver contacts is measured and obtained by utilizing the performance test platform of oil-immersed louver contacts. Based on the stress-strain curves of the stainless steel of the strap under different temperature conditions, a mechanical simulation model of the oil-immersed louver contacts was established. Based on this model, the effects of the plastic deformation temperature of the louver contacts and the stainless steel keel structure on the heating power of the strap are investigated. The results show that the mechanical properties of the louver contacts decrease with the increase in temperature, and the permanent plastic deformation of the strap occurs when the operating temperature reaches 400 °C. Appropriately increasing the torsion angle and thickness of the stainless steel keel can slow down the local overheating of the louver contacts caused by eccentricity. The research results are helpful to understand the mechanism of local overheating failure of oil-immersed electric contact parts, and provide a reference for the design, fault analysis and further research of oil-immersed electric contact parts.