Determination of the transition resistance of detachable electrical contacts with Camital active grease

Problem. The reliability of detachable electrical contact connections is significantly reduced due to an increase in transition electrical resistance caused by thermomechanical deformations, oxidation of contact surfaces, and a decrease in the effective contact area during operation. According to the results of operational and experimental studies, failures associated with contact degradation account for up to a third of the total number of electrical installation failures. Traditional methods, in particular the use of passive conductive lubricants, mostly only slow down oxidation processes and do not ensure active restoration of the contact condition. In this regard, it is important to develop models and technical solutions capable of describing and ensuring the stabilisation of the transition resistance of electrical contacts through controlled thermomechanical processes in the contact zone. Goal. To establish the regularities and interrelationships of processes in electrical contacts through experimental research and mathematical modelling of the evolution of the transition resistance of contact connections with composite grease modified with Cu–Al–Mn (Camital) with shape memory, taking into account the interaction of electrical, thermal, thermomechanical and tribological processes in normal and emergency operating modes. Methodology. Experimental studies were performed on models of bolted contact connections of aluminum busbars using composite grease containing 5 % and 10 % Cu–Al–Mn powder by volume, as well as on control samples without grease. Long-term measurements of contact resistance were carried out at a constant temperature and under periodic thermal loads. The theoretical study is based on a multilevel mathematical model, the numerical solution of which was carried out using implicit stable methods with parameter identification based on experimental data. Results. A decrease and stabilisation of contact resistance was established when using composite lubricant, most pronounced at a Cu–Al–Mn powder content of 10 % by volume. A reduced model of contact resistance evolution was proposed. Scientific novelty. For the first time, a generalised mathematical model of a detachable electrical contact with active composite lubricant has been developed, which takes into account the phase transformations of Cu–Al–Mn alloy particles and the mechanism of thermomechanical destruction of oxide films. The possibility of a step-like decrease in contact resistance under impulse currents is shown. Practical value. The results obtained can be used to improve the reliability of detachable electrical contact connections, predict changes in contact resistance during operation, and justify the choice of the composition of active electrical contact lubricants. References 37, tables 4, figures 7.