Stress Control Methods on a High Voltage Insulator: A Review

Abstract

This review article provides a comprehensive overview of the many factors that may enhance the level of electric field along the high voltage (HV) insulators, review of existing stress control methods and new promising technologies in stress control using advanced materials. In the first section, the factors that could possibly raise electric field stress around the HV insulators are discussed. Localized field enhancement, especially in the area close to the high voltage potential and ground potential will accelerate the degradation and subsequently causing pre-mature failure of the insulating material. Other than electrical field enhancement, mechanical stresses and environmental impacts also affect the performance of the high voltage overhead insulators. Consequently, multi-facet approaches are required to improve the HV insulators performance and reliability over their service life. In the second section, the existing stress control methods that include corona ring, combined insulation assembly and end-fitting design are reviewed. In the final section, a new promising technology of stress control using field grading methods (resistive and capacitive) is presented. Field grading material (FGM) is a new technology where the inorganic fillers are added to the insulation host matrixes to enhance the mechanical and electrical performance of the insulation. FGM shows superior electrical performance compared to the conventional insulation material, which is also discussed in this paper.