Multiple electrode probe assemblies and nondestructive testing of high ampacity joints

Two of the major impediments to accurate measurement of the electrical resistance of high-ampacity joints are the sensitivity necessary for measurements generally in the micro-ohms and the degree of current distribution control required. The authors have obtained accurate and reproducible results with multiple electrode probe assemblies and a micro-ohmmeter specially developed for the purpose. Two applications of the technique are described: detection of off-centering of the sleeves of 735-kV overhead transmission lines and braze control of the multiple conductor bars in high-power transformers and AC generators. The measurements obtained with the technique reflect both the mechanical strength and the electrical quality of the joints tested