Grounding concept considerations and recommendations for 400VDC distribution system

400VDC is becoming a new voltage interface for telecommunication buildings and data centers as well as for ICT equipment. 400VDC interface covers applications for up to 400VDC with a typical nominal voltage of 380VDC. Key drivers for utilizing a higher DC voltage are overall efficiency and reliability gains vs present solutions. However, introduction of a new 400VDC interface brings up some questions about personnel safety and implementation of system grounding. Although DC is considered safer than AC, till now datacom operators have been hesitant to deploy 400VDC because it´s not as commonly used and well understood as AC. This paper addresses 400VDC grounding issues and recommends high resistance midpoint grounding concept, as an effective way to provide safe operation of 400VDC distribution systems. Today Europe, North America (NA), and Japan telecom/datacom installations employ slightly different grounding concepts, practices, codes, or regulations. This paper also reviews different grounding models and their implementation praxis in Europe, NA, and Japan. Benefits and the disadvantages of different grounding concepts are discussed and explanation of the reasons for selection of high resistance midpoint grounding as a preferable model for 400VDC distribution system is provided.