A Comprehensive Comparison of Data Center Busbars and Row-Head Cabinet Power Distribution Systems

The data center busbar system is the common term for the end-of-line busbar power distribution system in data centers. The designation “data center busbar” simply reflects the fact that, compared with the low-voltage outgoing busbars at a substation or the main trunk low-voltage busbars in conventional large buildings, the individual busbars in a data center have a smaller current-carrying capacity. This paper presents a comparison of the technical performance between busbar systems and rack-mounted distribution cabinet–based power distribution systems; it further elaborates on the characteristics of busbar systems through case studies and provides a detailed life-cycle cost analysis of both rack-mounted cabinet distribution and busway distribution solutions. These findings can serve as a reference for engineering and technical personnel involved in data center construction when designing cabling systems.

I. Busbar System and Feeder Switchgear
　　The data center busbar system is the common term for the end-of-line busbar power distribution system in a data center. The “data center busbar” is simply a smaller-capacity single busbar compared with the low-voltage outgoing busbars at a substation or the main low-voltage trunk busbars in traditional large buildings. Typically, the upstream end of such a busbar connects to the main busbar, and through circuit breakers housed in busbar tap-off units, it links to the PDUs in each IT cabinet, thereby forming the data center busbar’s end-point power distribution system. The current rating of these busbars generally ranges from 100 to 400 amperes.
　　A data center row-end cabinet is a power distribution cabinet typically located at the head of a row of IT racks, serving as the terminal distribution unit for power distribution and protection to one or more rows of IT racks. Row-end cabinets are usually connected in a radial distribution configuration to upstream distribution cabinets, or in a trunk-and-branch configuration using a main busbar to connect to upstream power distribution cabinets. Each output circuit breaker in the row-end cabinet is linked to the PDU of each IT rack, forming the traditional end-of-line power supply and distribution system in data centers. Typically, the rated current of each row-end cabinet ranges from 100 to 400 amperes.
II. Comparison of Technical Performance Between the Busbar System and the Switchgear Cabinet Power Distribution System
　　(1) Advantages and Disadvantages in the General Sense
　　The busbar power distribution system in data centers is a typical trunk-type configuration, in which a single main feeder connects the central distribution cabinet to each server rack. Its advantages include lower material consumption for metallic conductors, rapid and convenient installation, plug-and-play operation, easy scalability and reconfiguration, higher reliability and longer service life compared with cables, as well as the ability to be reused. However, a failure in the main feeder can have a wide-ranging impact.
　　The power distribution system in the form of a row-end cabinet in a data center is a typical radial power distribution configuration, in which the main distribution cabinet directly supplies power to the row-end cabinets and their associated loads. Its advantages include independent power supply for each load, such that any fault is confined to the affected circuit and does not impact other circuits, thereby fully meeting the technical requirements stipulated by current national codes for critical electrical loads. However, this configuration also has several drawbacks: a large number of circuits, substantial consumption of metallic conductors, and complex installation. Moreover, the system exhibits poor flexibility—it lacks the ability to be reconfigured, makes phased implementation challenging, and cannot be reused. In addition, in a row-end cabinet–based power distribution system, the row-end cabinets occupy valuable space within the rack rows.
　　(2) Pros and Cons in Data Center Scenarios
　　Higher-grade data centers employ dual-circuit, mutually redundant power distribution at the IT equipment level.

Tier‑A data centers employ a 2N power distribution architecture, in which two independent and mutually redundant power supply systems deliver power to all loads via two separate power distribution circuits. Lower‑tier data centers, by contrast, typically use an N+1 redundancy configuration, where a single power supply with a certain degree of redundancy provides power to all loads through two independent power distribution circuits. Both architectures are characterized by their independence from any single circuit. Consequently, in trunk‑type power distribution systems—where the busbar serves as the typical representative—the significant drawback of extensive service disruption in the event of a trunk‑line failure is substantially mitigated.
　　Compared with other applications, data center deployments are characterized by significant uncertainty—both in terms of regional power supply capacity and the timeline for commissioning. Traditional rack-mounted switchgear-based power distribution systems are typically designed and implemented on a one-time, “right-first-time” basis, based on projected requirements. When actual deployment scenarios or commissioning schedules deviate from these projections, the system is difficult to modify, creating vulnerabilities in meeting real-world needs while controlling capital costs.
　　After mitigating the issue of extensive service disruption caused by trunk-line faults, data-center busbar power distribution systems are well-suited to the highly uncertain and variable conditions typical of modern data centers. They offer inherent advantages in on-demand, flexible configuration; phased deployment aligned with project rollout schedules; and seamless reuse of existing infrastructure following modifications. As a result, some enterprises have already begun exploring a business model centered on leasing data-center busbar solutions. Moreover, these systems do not occupy floor space, enabling maximum utilization of precious data-center real estate for core operational applications.
III. Case Analysis
　　(1) Project Status (Virtual)
　　Data Center Construction Plan: The data center is planned to cover an area of 1,300 square meters, with 600 square meters being constructed in this phase (the remaining area reserved for future expansion). A total of 169 IT cabinets will be available in this phase, with cabinets typically arranged in rows of 12 or 18.
　　Each 600-mm-wide cabinet is rated at 3–5 kVA and equipped with two 32-A single-phase APDUs.
　　Data center power supply mode: row-end cabinet power distribution.
　　The row-end distribution cabinets are designed with dual-circuit power supply, with inputs from UPS’s A and B power feeds. Power is distributed from the A/B-row-end cabinets to each IT cabinet via underfloor cable trays, with individual cables routed to each cabinet and connected to the industrial connectors on the in-cabinet PDUs to provide power.
　　4 kVA per cabinet, with a total power of 4 kVA × 18 = 72 kVA for 18 cabinets (109 A per phase). The row-end distribution cabinets are configured as 160 A/3P × 2 for input and 32 A/1P × 21 circuits × 2 units for output (each unit serving 18 circuits plus several spare circuits).
　　② Power Supply Characteristics of the Headroom Cabinet
　　• Adopts the traditional centralized power distribution scheme at the row head, with one high-voltage row-head cabinet installed on one side of each row of cabinets;
　　• A large number of power supply cables are laid in a radial configuration, connecting the row-end distribution cabinets to each individual cabinet;
　　• A power cable trunking must be installed beneath the cabinet, which entails substantial construction effort and relatively cumbersome future maintenance. Moreover, the presence of the trunking can adversely affect the underfloor air distribution of the data center’s HVAC system, limiting the system’s flexibility for reconfiguration.
　　(2) Data Center Power Supply Mode — Busbar Scheme
　　① Replace the row-end cabinets with a busbar scheme.
　　Two rail-mounted busbars, each equal in length to the cabinets, are installed at the top of each cabinet row. The A and B feeds from the UPS output are distributed to individual IT cabinets via plug-in busbar distribution units mounted on the top of the cabinets, which connect to the cabinet’s A/B feed PDUs to provide dual-power supply to each cabinet. The location of the busbar distribution units can be flexibly adjusted and configured based on the placement of the cabinets.
　　4 kVA per cabinet; with 18 cabinets, the total power is 4 kVA × 18 = 72 kVA at 109 A; each cabinet is rated at 4 kVA/18.18 A; the busbar specification is 160 A with a length of 10.8 m; six output plug-in distribution boxes are provided (each with three circuits, each rated at 25 A).
　　② Characteristics of the busbar scheme
　　• No extensive cabling is required; power can be supplied locally via plug-in distribution boxes (whose positions are adjustable). The PDU plugs in IT cabinets can be directly inserted into the busbar distribution box, eliminating complex wiring.
　　• The cabinet’s power supply has been changed from the original underfloor distribution to a top-mounted distribution configuration. This eliminates the need for power cable trays beneath the floor and on top of the cabinets, while also reducing airflow resistance in the data center’s air-conditioning system.
　　• Supports on-demand (hot) expansion of circuit count, offering high adaptability to changing requirements;
　　• The power supply system is simple and easy to maintain. Two busbar trunking systems—busbar sections A and B—are installed on each cabinet row.
　　(3) Comparison of the Mini-Busbar System with Traditional Rack-Mounted Switchgear
　　① The busbar exhibits high flexibility.
　　Traditionally, power distribution is implemented by connecting a UPS output cabinet to a row-end distribution cabinet, which then supplies power to the equipment in each rack via individual cables. This radial power distribution architecture entails one-to-one cable connections between each rack and the row-end distribution cabinet; consequently, any future additions, rack expansions, or power upgrades necessitate re-routing of the cabling. In contrast, busbar trunking systems offer a simple and rapid deployment: the busbar trunking is simply installed above all intended racks—whether currently deployed or planned for future installation—thereby completing the rollout. This approach enables on-demand installation as users move in, aligning with their specific needs. Moreover, when individual racks require increased output capacity or additional circuits, no modifications to the busbar trunking are necessary; it suffices to add or replace plug-in units (which support hot-swapping), making this solution well-suited to the uncertain growth trajectories of IT operations and ensuring that planning can keep pace with future changes over the long term.
　　② The busbar increases the utilization rate and revenue of the data center.
　　By adopting a busbar distribution scheme, the need for a dedicated power distribution cabinet at the row level is eliminated, allowing one additional IT cabinet to be installed in the original location of that cabinet. Typically, one power distribution cabinet is provided for every 20 IT cabinets; eliminating this cabinet enables an increase of approximately 1/20 in the number of IT cabinets. Taking a data center with 1,000 cabinets as an example, the original requirement would have been 50 row-level power distribution cabinets; with the busbar solution, the data center can accommodate up to 1,050 IT cabinets. Assuming a rental fee of RMB 60,000 per cabinet per year, this change would generate an additional annual benefit of RMB 3 million.
　　
　　③ The busbar has a long service life and is reusable.
　　The track-mounted precision busbar boasts a long service life of 20 to 25 years or more. Its modular, plug-and-play design enables repeated disassembly and relocation, thereby maximizing protection of the user’s capital investment and indirectly enhancing the system’s value. In contrast, conventional distribution switchgear cabinets combined with cabling typically have a service life of only about 8 to 10 years, and once expanded or relocated, neither the cabinets nor the cabling can be reused. Consequently, the busbar trunking system offers a service life that is more than two to three times longer than that of the switchgear cabinet system and can be repeatedly reused, significantly reducing long-term operating costs.
　　④ Rapid system deployment and short construction period
　　The rail-mounted busbar system enables rapid installation and deployment. In contrast, the conventional approach of using rack-mounted switchgear combined with cable routing typically requires 30 to 40 days to complete a typical data center project, involving numerous time-consuming steps such as positioning distribution cabinets, installing cable trays, cutting and laying cables, and splicing cable connections. By contrast, deploying a busbar system can deliver a fully commissioned data center in just 7 to 10 days, significantly reducing construction time and labor costs while also eliminating the need for cable trays and extensive cabling. This allows for nearly one month earlier delivery to the customer.
IV. Evaluation
　　① Without considering the financial cost implications of phased construction, the busbar solution incurs a 20% higher cost per rack in the IT terminal power distribution stage compared with the row-end cabinet solution.
　　② Considering financial costs, assume that 50% of the project will be put into operation immediately, while the remaining 50% will be commissioned one year later. Under the switchgear cabinet solution, the entire investment of RMB 10.8657 million would be made upfront; under the busbar solution, 50% of the investment—RMB 7.16098 million—would be committed initially, resulting in a reduction of over RMB 3.7047 million in initial outlay. Based on an annual loan interest rate of 7%, the one-year financial cost would be reduced by more than RMB 259,000.
　　③ By adopting a busbar system, the data center has added 182 IT cabinets. Assuming a leasing fee of RMB 60,000 per cabinet per year, this will generate an additional annual revenue of RMB 10.92 million. With a profit margin of 20%, the incremental annual revenue amounts to RMB 2.18 million, meaning the additional capital investment for the busbar solution can be recouped within two years.