Electric Field Analysis at Triple-Joints and Localized Defects on Different Composite Insulators Designs

Composite insulators have been extensively employed around the world due to their lighter weight, improved performance in harsh environments, and potential lower maintenance costs. However, brittle fracture caused by stress corrosion cracking may occur due to water penetration into metal end fittings during operation, even under lower mechanical loads, possibly leading to a complete failure of the composite insulator. Given that the electric field may play a role in brittle fracture of composite insulators in form of partial discharges, two of the most common existing designs that result in different locations of the triple-joint - interface consisting of metal end-fitting, air, and polymer - are studied. The electric field intensification at the triple-joints is modeled using finite element modeling and validated by analytical calculations. In addition, as another recurrent physical defect in composite insulators, air voids are assessed in different locations of the analyzed composite insulator designs to determine their criticality on brittle fracture mechanism. Results present the optimal design based on the location of the triple-joint in composite insulators, and the most critical locations where air voids may severely contribute to failure modes in the composite insulators.