Causes and potential remedies of brittle fracture failure of composite (nonceramic) insulators

Existing brittle fracture models have been reviewed and their applicability to explain the in-service brittle fracture failure of composite (nonceramic) insulators is evaluated. It is shown that the only brittle fracture model that can explain all aspects of the brittle fracture process is a model based on the formation of nitric acid solutions in-service. The chemical cause of brittle fracture is identified in this work and recommendations are made on how to avoid brittle fracture in-service by proper selection of composite insulator rods resistant to brittle fracture. An attempt is made to clarify misconceptions that exist in the literature regarding the causes of brittle fracture and the most suitable prevention methods.