“Brittle fracture” of composite insulators: why and how they occur

Many studies have been performed to show that the source of the acid that could produce brittle fractures in service was associated with electrical discharges. The paper shows that, although possible, this mechanism is not compatible with many observations of failed insulators. This study shows that the materials and process used for the impregnation of the glass fibers of the FRP rod can lead to the presence of acid particles that will become part of the rod. Tests have been conducted using acids derived from a rod manufacturing process. Typical brittle fractures have been obtained with insulators made with commercially available rods. This source of acid explains the brittle fractures obtained in service and agrees with the examination of failed insulators. It also explains why insulators that should have been vulnerable have not failed