Detection of Local Softening, Welding and Formation of Metallic Bridges between the Copper Contact Pair Using Temperature Measurement

A paper is focused on the analysis of local softening, welding and formation of metallic bridges between the copper contact pair using temperature rise measurement. The contact pair is one of the most important and, at the same time, most problematic parts of the current-carrying path of electrical switching apparatuses, because of its power losses. Amount of power losses is mostly affected by a contact force and by a type of used contact material. Inappropriate choice of these parameters could lead to the extreme heating of contact pair and whole device. A material of contact is affected by a high temperature. Phenomena called local softening and welding may occur due to the high temperature. Metallic bridges create a permanent connection between the contacts. This permanent connection decreases a contact resistance, but unfortunately it disables the function of the entire switching device - the ability to break the electric circuit. The paper shows one of the possible solutions to the problem with on-line detection of phenomena between contact pair using temperature rise measurement.