Facility-level DC vs. typical ac distribution for data centers: A comparative reliability study

This paper presents a comparative reliability analysis of a dc power distribution system in a range of 400 Vdc at the facility level against a typical ac distribution, for critical data-center loads. Assumptions and conditions are established to allow meaningful comparisons. Inherent availability and survival function are used as the two reliability metrics. Analytical reliability models for various common configurations are developed, and quantitative results are obtained based on a set of generic reliability data. The study indicates that the dc system would be more reliable than the ac to a certain extent when considering a configuration with multiple units of uninterruptible power supply and loads but without redundancy. However, on a large scale with redundancy, it is shown that the dc would have a similar reliability level to that of the typical ac distribution.