Three-wire DC distribution to telecommunication equipment

This paper takes a new look at the -48 V power distribution widely used for providing power to telecommunication equipment, and at the methodology used for grounding and bonding of both the power system and the powered telecommunication system. In contrast to AC distribution, the DC distribution used in telecommunications and its associated grounding are not extensively covered in electrical codes such as the National Electrical Code and the Canadian Electrical Code, or in international standards such as IEC 364. The paper identifies analogies and differences between the experience-based, codified requirements for single-phase DC systems and the evolving requirements for DC powering and system grounding used in telecommunications. It suggests that the harmonization efforts of evolving national, regional and global standards for these DC systems could benefit from a critical examination of the proven principles developed for AC distribution