A Study on the Application of SPDs in Low-Voltage DC Systems for Consumer Installations

With the growing interest in low-voltage direct-current (LVDC) systems, various types of new electrical equipment are being introduced, increasing the need for technical research and revisions to relevant installation requirements. However, from the perspective of electrical safety, adequate requirements have not yet been established for either newly introduced or existing equipment in LVDC systems. Surge protective devices (SPDs) are widely used to protect electrical installations against transient overvoltages caused by lightning and switching events and are also applied in DC systems. Nevertheless, detailed requirements for the selection and installation of SPDs considering DC system configurations and grounding arrangements remain insufficient. Therefore, this study investigates appropriate SPD installation methods for DC systems by analyzing SPD connection schemes according to system configuration and grounding arrangement, as well as the selection of impulse discharge current ratings. Conventional SPD installation methods used in AC systems were analyzed and adapted to DC systems, and the impulse-current sharing characteristics in two-wire and three-wire DC systems were experimentally evaluated. Based on the analysis and experimental results, suitable SPD application methods for different system configurations and a method for selecting the required impulse discharge current rating are proposed. The findings provide practical guidance for applying SPDs to DC installations, whose electrical characteristics differ from those of conventional AC installations, and can serve as a basis for establishing safer installation requirements for LVDC systems.