With the development of power business and the upgrading of smart grids, the requirements for the reliability and intelligent maintenance of power supply systems in power data centers are becoming increasingly high. The power distribution design on the side of data center cabinets should not only meet the power distribution functions of traditional computer rooms, but also meet the long-term equipment expansion needs; Meanwhile, efforts should be made to minimize the impact of equipment expansion on already operational devices. In addition to meeting high reliability, the power supply system should also have powerful monitoring functions. The operation and maintenance personnel in the computer room can always understand the load status of the cabinet, the electrical status of each distribution branch, and the power consumption of different load groups

The capacity is generally maintained within a certain range, usually according to server cabinets, blade cabinets, network cabinets, work cabinets, small computer cabinets, etc. The load of a single cabinet in a conventional data center is generally between 3-8kW. According to the different power of various devices, the interface standards of electrical connectors are also different, which poses challenges to the implementation of power supply infrastructure. The traditional floor standing distribution unit (column cabinet) can no longer meet the growing demand for power supply.

In recent years, with the flexible and diverse development of data centers, a more flexible cabinet side design has gradually been applied to power rooms, namely busbar distribution systems. At present, a large number of large-scale data centers have purchased bus duct design solutions, such as Google, Facebook, Alibaba, Tencent, etc. Busbar trunking, as a wire application in the power industry, has a history of several decades. However, for the application of power data centers, it is still relatively new and there are not many application cases. Compared with traditional cable methods, bus ducts have more reliable safety and superior interface resistance and temperature rise control.

1、 Principle of Busbar Duct Structure

Bus duct is a closed metal device composed of copper and aluminum busbars, used for decentralized systems. Allocate more power to the components. Busbar is a new type of conductor formed by using copper or aluminum as a conductor, supporting it with non olefin insulation material, and then encapsulating it in a metal groove. The rated voltage of the computer room bus duct is 380V, suitable for three-phase four wire or three-phase five wire power supply and distribution projects with AC 50Hz and rated current of 250-6300A. It has the characteristics of large capacity, easy disassembly and assembly, and short construction period

(1) Classification development

Bus ducts are generally divided into starting bus ducts, straight through bus ducts, L-shaped vertical bend bus ducts, Z-shaped vertical offset bus ducts, T-shaped vertical three-way bus ducts, X-shaped vertical four-way bus ducts, as well as related accessories and fastening devices. Solid devices. According to the insulation method, plug-in bus ducts are divided into three types: air type, dense type, and high-strength. According to their structure and purpose, they can be divided into dense insulation, air additional insulation, air insulation, fire-resistant insulation, etc; According to the shell material, it is divided into steel shell, aluminum alloy shell, and steel aluminum mixed shell bus duct.

The development of bus ducts has gone through three generations. The first generation is air type bus ducts, the second generation is dense bus ducts, and the third generation is composite insulated bus ducts. The development technology of bus ducts is becoming increasingly sophisticated and mature.

(2) Advantage analysis

Bus ducts use copper or aluminum as conductors, with high current capacity and good electrical and mechanical performance. The casing of the bus duct is made of metal, non flammable, safe, reliable, and has a long service life. Compared with traditional cables, pipelines or bridges occupy less space, which is very advantageous for the construction and cable layout of large buildings.

The main characteristics of busbar trunking are as follows:

① Large capacity, low voltage drop, strong short-circuit load capacity;

② High reliability;

③ Small in size, aesthetically pleasing in appearance, and lightweight;

④ Easy construction connection and simple inspection.

2、 Computer room bus duct

The busbar trunking system in the power room consists of six parts: the main body of the main line, the end feeder module, the main line connection module, the junction box, the monitoring module, and the communication module.

(1) Main trunk line

The outer shell of the bus duct provides air duct protection, improves thermal stability, and meets various installation methods such as vertical lifting or horizontal installation, with markings on the side. Conductive copper bars are electrolytic copper with different cross-sections, plated with tin on the surface to enhance corrosion resistance and reduce contact resistance based on current carrying capacity. Surface insulation materials have good short-circuit current capability.

(2) End feed module

The terminal feeding module is used to connect the power supply to the busbar system. The terminal feeding module is equipped with built-in circuit breakers, monitoring modules, and communication modules. The specifications of the circuit breaker are configured according to the load requirements of each column.

(3) Bus duct connection module

The bus duct connection module is used for the connection between the terminal feeding module and the bus duct body, between the main bodies of the wire ducts, and between the main bodies of the bus ducts. Main body and elbow of conduit

(4) Junction box

The junction box can be installed on the main body of the bus duct. The junction box is equipped with control circuit breakers and sockets for supplying power to the cabinet. Currently, in the industry, junction boxes are installed on the main body of bus ducts. Most of them support hot swapping and flexible card slot fixation. Convenient to provide electrical connections for expanding loads at any time. There are two design scenarios in the industry for the specific installation position of the junction box on the main body of the bus duct: fixed installation and flexible installation. Schneider and other suppliers use fixed position installation, which means reserving an installation hole every 600mm on the main body of the busbar duct to provide junction box installation. Suppliers such as CESKO and CG BUSWAY can install it at any position on the main body. For the placement of cabinets of different sizes, the latter is undoubtedly more suitable for the design of the computer room

(5) Monitoring module

The monitoring module is divided into two parts: the terminal and the main control unit. The terminal unit is the bus duct of the computer room. Electrical data such as power, current, voltage, etc; The main control unit includes a hardware main control unit and a software management platform

(6) Communication module

The communication module basically supports mainstream communication methods in the industry in terms of mode, and some manufacturers also support copper wire and wireless media SNMP management. The intelligent management room adds busbars

3、 Bus duct design

This article takes a 300m2 motor room as an example to compare the design of busbar trunking scheme with traditional head cabinet scheme. This area can accommodate 9 rows of cabinets, with each row supplying power to the nearest two rows of cabinets. The size of each cabinet is 800mm x 1100mm, as shown in Figure 1.

Option 1: Suspended double bus duct with one row of power cabinets. The junction box on each bus duct is equipped with two air switches and two industrial sockets to supply power to the cabinets on both sides of the row. Support plug and play, simple and convenient. Business expansion and functional expansion.

Option 2: If the traditional head cabinet distribution scheme is adopted, two rows of cabinets must be equipped with one head cabinet, and each cabinet must be powered by dual power sources, as shown in Figure 2.

(1) Main body

The average power of each cabinet configured with bus ducts is calculated based on the final demand of 6kW. According to the layout, there are 8 cabinets in each row of the computer room, with a power of P=8 x 6kW=48kW and a long-term working current of/=48/(0.8 x 3 x 0.22)=90 (A)

The cross-section of the busbar should generally be selected based on the long-term operating current. When the average load is high and the bus distance is long, it is generally better than the long-term working current. The cross-section of the selected bus duct should be relatively large. This situation is characterized by high annual load and long distance. The specification of the end bus duct is configured according to 160A, that is, each row of cabinets is equipped with 2 160A bus ducts, which are respectively connected to the main and backup UPS. As shown in Figure 3.

(2) End distribution module configuration

The end feeding module is connected to the distribution box through the main and backup bus ducts corresponding to each row of cabinets, and is used for cable connection between the plug-in boxes of the main bus ducts.

(3) Cabinet

The side feeder box is used to install cabinet side feeder boxes on the main and backup busbars. Server cabinets and storage cabinets are equipped with 32A switches, while workstation cabinets and network cabinets are equipped with 16A switches. Connect the industrial connector to the PDU row on the cabinet.

(4) Monitoring system collection

Functions include switch status, power, power, power factor, voltage, etc. The communication function is to open the interface of the computer room power environment monitoring system through the terminal bus duct power supply monitoring platform, and provide monitoring data

(5) Bus duct grounding

The traditional protective grounding wire PE is placed on the inside of the bus duct, while the new type of bus duct adopts a PE integral grounding shell. According to Article 5 of the mandatory standard GB7251.1 for electric shock protection 7.47.4.3.1, if the measures taken can ensure that the circuit has good conductivity and the current carrying capacity is sufficient to withstand the grounding fault current flowing in the complete set of equipment, various metal components of the assembled complete set of equipment should be considered to ensure the continuity of the protective circuit.

4、 Scheme comparison

The differences and comparative analysis of the advantages and disadvantages between the busbar trunking technology in Scheme 1 and the traditional head cabinet scheme in Scheme 2 are as follows:

⑴ Technical comparison

① Heat dissipation

The busbar trunking in the computer room is different from the traditional dense busbar trunking in China, and adopts an open design. In terms of design, the current carrying copper bar is in direct contact with air, utilizing air conduction to dissipate heat, and dissipating heat through a tightly connected steel shell. In addition, the aluminum shell of the bus duct has a protective effect, and the surface has also been anodized to enhance heat dissipation capability; Nickel plating on the surface of copper bars reduces contact resistance, voltage drop, and losses. In the traditional method of adding cables to the front cabinet, the insulation material of the cables is both insulating and heat-insulating. In the case of a large number of cabinets, cables will gather more and heat dissipation will be difficult. So, when laying power cables inside the bridge, in order to ensure good heat dissipation, it is generally allowed to lay 2 layers. Therefore, the heat dissipation performance of bus ducts is superior to that of cables.

② Maintainability

Traditional cable methods require regular inspection and maintenance due to factors such as material wear and aging, short lifespan, etc. They also need to be replaced at the end of their service life. The bus duct is a metal structure, which is easy to maintain. Daily maintenance usually only requires measuring the temperature rise of the shell and core bolts, as well as the temperature rise of the inlet box joint.

③ Overload capacity

The normal working temperature of the insulation material used in the cable is 95-105-C, and the overload capacity of the bus duct is much higher than that of the cable. In addition, the current carrying range of the cable is 1000mm, the cross-sectional area is 1600A, and the rated current is 1600A, while the rated current of the bus duct can reach 6300A.

④ Space layout

The spatial layout of bus ducts can save space occupied by distribution cabinets or column cabinets, and avoid the use of cables, thereby reducing wiring difficulty. Taking Figure 1 as an example, 6 column cabinets can be saved.

⑤ Design and installation

Simple, easy layout, simple installation steps, no need for tools.

⑥ Expansion and Total Cost of Ownership (TCO)

After installation, the bus duct can be reconfigured as needed, and capacity can be reserved during design. Future expansion is convenient and the total cost of ownership is lower.

⑦ Environmental protection characteristics of bus duct

All materials are made of flame-retardant materials. 0.99 material is recyclable and has better environmental characteristics, while cables have a certain degree of pollution

(2) Investment Comparison

The comparison of investment costs for the different cabinet end distribution schemes of Scheme 1 and Scheme 2 is shown in Table 1. Comparing the total cost of head cabinets, cables, cable trays, etc., the total investment design scheme for bus ducts is quite basic compared to the traditional cabinet plus cable method, but the latter has lower maintenance costs and overall lower ownership costs than cables.

conclusion

Bus ducts have flexibility and scalability. The same bus can be flexibly configured according to different cabinet load sizes (similar to network bandwidth sharing, power load sharing); If expansion is needed, adjust the phase (three-phase unbalance time) and adjust the corresponding plug-in box accordingly. The busbar trunking scheme in the computer room is a way to reduce cable usage and has practical application significance for electrical rooms in centralized power supply systems. With the development of smart grids and big data services, the application of power data centers has been increasing year by year in the construction process of power data centers, which is also a development trend. Bus duct has stable and reliable performance, high distribution efficiency, good heat dissipation, low voltage, resistance to mechanical shock, and easy installation. It is a good terminal power supply method for power data centers.