Statistical Analysis of String Fracture and Core Breakdown of Composite Insulators in Zhejiang Province

Composite insulator string fracture and core breakdown failure pose serious threat to the safe and stable operation of transmission lines. This paper analyzes string fracture and core breakdown accidents in Zhejiang Province since 2016, including failure overview, product condition, failure pattern, performance test, failure cause analysis, and related recommended measures. The results show that there are eight composite insulator broken strings and core breakdown failures in Zhejiang Province since 2016, including six decay-Like fracture, one brittle fracture and one core breakdown. Among them, the brittle fracture is caused by weak end seal, the external moisture enters, lead to stress corrosion under long-term high electric field; the decay-Like fractures failure is mainly caused by poor bonding of the core housing, and under combination of damp, discharge and mechanical stress, The epoxy resin matrix in the core is degraded and deteriorated; the core breakdown is caused by partial bonding of the interface, the housing or the end seal is broken, and the moisture enters the interior along the interface or the defect of the core, causing partial discharge to form carbonization. The passage, and gradually developed into a penetrating breakdown. In view of the above failures, it is recommended that the composite insulator ends are connected by coaxial multi-directional crimping, the end seals are sealed with high temperature vulcanized silicone rubber, and the core is made of boron-free fiber resistant acid core with good stress corrosion resistance, and bonding strength of the interface is ensured. What’s more, infrared and ultraviolet detection of the composite insulator are suggested during the operation and maintenance process.