Type Designations of Stem Insulators for AC 25 kV Catenary and Suitability Analysis of Insulation Distance

There are a total of 17 types of 25 kV AT-type catenary insulators, which can be categorized into suspension, stem, and support insulators. Their materials include glass, ceramic, and polymer. In the first phase of the Gyeongbu High-Speed Railway, insulators of a 46 kV insulation class made of glass were installed for the 27.5 kV rated system. In contrast, in the second phase of the Gyeongbu High-Speed Railway and in the Honam High-Speed Railway catenary, newly developed polymer insulators are adopted. In particular, the T-mx polymer insulator was designed to maintain the overall dimensions of the existing glass insulator while enhancing electrical performance for the movable bracket. However, railway operations in the field have requested further improvement in the polymer insulator’s insulation performance to mitigate frequent flashover accidents. Therefore, this paper examines the type indication of AC 27.5 kV catenary insulators and reviews the suitability of the insulation distance, including creepage distance, for a 46 kV polymer stem insulator.