The electrical interface systems currently used for external power supply to railway vehicles are primarily based on the UIC 552 and UIC 554 standards developed in the 1970s. These standards address only the transfer of electrical energy and no longer meet the demands of modern railway applications. Their limitations include manual meter readings that hinder efficient billing, reliance on physical identification tokens considered impractical by users, the absence of automated load management during peak demand, and the lack of support for vehicle-to-grid energy feedback. To address these challenges, this paper examines the potential application of road vehicle charging standards—specifically ISO 15118—to railway applications. The proposed approach begins with theoretical analyses of existing railway infrastructure, evaluating its compatibility with digital charging protocols and identifying technical barriers and necessary adjustments. Railway-specific requirements are taken into account. In addition, the study considers emerging developments, including bidirectional charging, the evolution of the Open Charge Point Protocol, and the applicability of DIN EN 50546 for three-phase power supply at 63/125 A and 600 A. Furthermore, a power supply via the train line according to UIC 554 is evaluated. This investigation presents an implementation concept for ISO 15118 in railway applications, aiming to modernize railway external power supply systems and enhance efficiency, flexibility, and interoperability.