| Summary: | One SSY type equipment clamp serviced in a 500 kV station was found to be cracked. In this paper, the crcaked cause and mechanism is investigated by means of macroscopic morphology observation, fracture surface morphology observation, X-ray digital detection, metallographic observation. The results indicated that the main reason for the fracture of the equipment clamp this time is that the terminal board is a cast part, which contains a large number of casting defects such as porosity and shrinkage, resulting in a decrease in its effective cross-sectional area and load-bearing capacity. In addition, insufficient modification treatment of the terminal board led to insufficient toughness due to needle or rod-shaped eutectic silicon in the organization. Finally, under the combined action of dynamic load and self weight caused by the swinging of the wire in the wind, the terminal board was brittle fractured along the bolt hole with obvious stress concentration effect.
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