DC Distribution - Voltage Drop Criteria

The purpose of this paper is to explain why the dc distribution system for most telecommunication equipment employing emergency battery reserve should be considered as an integral part of the reserve system and how this concept can be used to develop distribution voltage drop criteria on an economic basis. It will then become clear that what seems to be an extravagant use of conductors is really the result of a trade-off between marginal battery and cable costs. A method is described for calculating the most economical distribution voltage drop. Since a large proportion of telecommunications equipment operates at a nominal -48 volts this paper will limit itself to a discussion of 48 volt distribution. Although there has been phenomenal technological development in telecommunications equipment the technology of distribution has not changed; we still use copper or aluminum conductors. However, there have been changes in system voltage limits and power plant configuration as a result of the technological change in load equipment. Also, distribution design has been re-examined.