Cause Analysis of the Crooked High Voltage End Fittings for a 220kV Composite Insulator in-service

The high voltage end fitting for an in-serviced 220kV composite insulator was found to be crooked by the transmission line inspector, and the deformed cause was then investigated by digital X-ray imaging, chemical composition analysis, metallographic observation and mechanical properties testing in this paper. The results indicated that both the material quality and mechanical properties of the composite insulator high voltage (HV) end fitting met the standard requirements. And the main reason for the crooking of HV end fitting was the effect of abnormal force, such as falling from high position, impact of heavy objects. At last, it was advised that the supervision on the installation quality of fittings and the inspection of in-service composite insulator fittings should be strengthened. In addition, composite insulator with deformed or fractured end fitting should be timely handled, avoiding similar metal section failures.