Various technologies have recently been developed for high-speed railways, in order to boost commercial speeds from 300 km·h⁻¹to 400 km·h⁻¹. Among these technologies, this paper introduces the 400 km·h⁻¹ class current collection performance evaluation methods that have been developed and demonstrated by Korea. Specifically, this paper reports details of the video-based monitoring techniques that have been adopted to inspect the stability of overhead contact line (OCL) components at 400 km·h⁻¹ without direct contact with any components of the power supply system. Unlike conventional OCL monitoring systems, which detect contact wire positions using either laser sensors or line cameras, the developed system measures parameters in the active state by video data. According to experimental results that were obtained at a field-test site established at a commercial line, it is claimed that the proposed measurement system is capable of effectively measuring OCL parameters.