Failure Analysis of Insulator Iron Cap in Low Stress State

The safe and stable operations of insulator components create an important issue, with massive constructions of high-voltage direct current (HVDC) projects. However, the service life of the insulator iron cap directly depends on the production process. Therefore, it is necessary to examine the quality of the products and clarify the causes of failure. Under equivalent conditions, the insulator iron cap, made of nodular graphite cast iron, failed when the load value reached 1929 kN by calculation, rather than 278 kN in this loading test. In this investigation, some of the defects were due to improper heat treatment process. When present, these defects eventually lead to fracture. The results of the research for the process design of insulator iron cap are available.