The ac/dc substation control equipment, pole control equipment, protection equipment, and auxiliary secondary equipment of high-voltage direct-current (HVDC) transmission systems are the focus of this guide. Based on analyzing the existing HVDC transmission projects, specifications for structure, configuration, performance and test of HVDC control and protection equipment, which could be applied to HVDC transmission system with the voltage range up to and including 800 kV are provided in this guide.