HVDC (High Voltage Direct Current) overhead transmission line was considered to prepare the interconnection between northeast Asian countries and inside power systems for the first time in Korea. For HVDC transmission lines, the corona discharge characteristics and space charge of conductors depend on the electric field conditions of the conductor, so transmission line designer have to estimate the electrical environmental effects such as radio, audible, and television noise from any set of conductors. In this paper, test method will be shown using reduced-scale test facilities of HVDC transmission line.