Cause of Fracture on Current Transformer Drainage Hoop Clamp of Current Transformers

The fracture of current transformer drainage hoop clamp was found in several substations in Yunnan Province. The causes of fracture on clamp were analyzed by means of macro analysis, chemical composition analysis, fracture analysis, metallographic inspection, mechanical property test and finite element analysis. The results show that the fracture mode of aluminum alloy and copper alloy hoop clamp is brittle fracture. The main reason was that the clamp was over tightened during installation, resulting in large stress concentration at the turning point of the structure of clamp lug. When the stress exceeded the yield strength of the material, the clamp fractured. Unqualified chemical composition and elongation after fracture of some copper alloy clamps were also important reasons for the fracture of this type of clamp.