Performance Analysis of Medium Voltage Porcelain and Polymer Cut-out Fuse Insulators under Lightning Impulse Wave Forms

Abstract

Insulation is critical to reliable power system performance, including medium voltage cut-out fuse insulators that are crucial to protecting outdoor distribution lines, transformers, and equipment. In case of medium-voltage networks, these insulators are primary protection from voltage flashover and breakdown that might result from impurities like dust, salt, industrial discharge, organic elements, and desert conductive pollutants. Damage to these insulators, however, can result in equipment damage, safety hazards, and blackouts. Recently, polymeric materials have been studied to replace the conventional porcelain insulators. The porcelain and polymer performance of soft relining materials is compared in the article. the work examines the dry FRP porcelain and polymeric cut-out insulators in 11 kV overhead lines to evaluate their performance under different types of lightning impulse tests, including clean and heavily polluted conditions. The study discusses positive polarity and critical flashover voltage (CFO), as well as the parameters of voltage-time waves, with the direct Strike using 1.2/50 µs and the Side Strike using non-standard 5/100 µs impulse shapes (with standard values). The laboratory experiments, carried out when heavy pollution was simulated, showed that the loss in mechanical strength reached 43.29% for porcelain and 14.39% for polymer under standard conditions and 51.82% for porcelain and 22.17% for polymer under non-standard conditions. This goes to show that polymer cut-out insulators have better performance than porcelain insulators. The dielectric properties of an insulator profile are heavily dominated by the effect of the lightning impulse voltage, and non-standard impulses expose them to more over-voltage stress than standard ones. This paper suggests that prototype testing should introduce non-standard impulses. The results set a baseline for future experimental work in this area.