Evaluation Method of Defect and Fracture Reason for Composite Insulator

Abstract

In order to analyze the reason of the fracture of a composite insulator in service in China Southern Grid,we investigated the appearance inspection,material test and anatomy of the AC 500kV line fracture composite insulator.The results show that the fracture is caused by long-term partial discharge between the core rod and housing,making the core rod serious aging,while the poor adhesion of the interface between the core rod and housing is the main reason for partial discharging.The eclipse hole appears on sheath surfaces under the action of long-term partial discharge.The aging of the core rod is intensified after the moisture enters,leading to the fracture of the core rod.For evaluating the adhesion between the rod and housing,a new five-class evaluation method was proposed.Using this evaluation method,six insulators in service were grading evaluated.Through the classification evaluation,it is known that there are two factors to affect the adhesion between the rod and housing of composite insulators:the adhesion quality of composite insulators during the manufacturing process and long-term high field strength.