Busway systems are a popular solution for effective power distribution. But data centre teams must be aware that not all busway systems are the same and safety must be a key consideration in selecting a vendor. Here, John Berenbrok, Senior Product Manager, Data Center Infrastructure at Starline, talks us through the safety aspects of various elements of a track busway system so organisations can make informed, safe choices.

For data centre owners and Consulting and Specification Engineers (CSEs), busway systems are rapidly becoming the solution of choice for effective power distribution. Track busways can be suspended from the ceiling, placed on vertical supports, or even mounted on the server cabinets themselves to provide a direct power source to servers and racks.

But not all busway solutions are the same; some work better, last longer and require less maintenance than others. In evaluating a busway solution, you should look for three important qualities:

• Reliability – An effective busway system provides reliable and efficient power distribution, a maintenance-free joint design and a long useful life, to ensure continuous uptime for your IT infrastructure.
• Flexibility – An effective busway system gives you flexible design and power distribution options, allowing you to build out, scale up and adapt your IT loads according to your changing power and facility needs.
• Safety – The elements of a busway system should guarantee safety for your workers, your IT infrastructure and your facility.

Here we will explore the individual elements of a track busway system, with a focus on ‘safety’.

The importance of safety

Safety of equipment is paramount in the data centre – first and foremost, to protect the workers who work there; secondly, to protect the IT infrastructure and the data that it processes; and finally, to protect the facility itself. Busway systems offer significant safety advantages over RPPs and greatly reduce the risks of dangerous incidents, such as electrical shocks and arc flash explosions.

Data centre owners have a responsibility to provide employees and electricians with the safest work environment possible. It’s crucial that owners and CSEs look for a busway solution that is designed for safety and is certified as safe.

Design elements of a busway system

There are four primary elements that make up a busway system. These are:

• Track busways
• Joints
• Plug-in units (or tap boxes)
• Power monitoring

You should look for a busway system that includes multiple provisions to deal with potential arc flash scenarios. The solution should have the following:

• Certifications from nationally-recognised test labs
• Selective coordination of fuses which, in the event of a power surge, allows the busway system to lower potential incident energy to negligible levels
• Arc flash certifications that include operator and equipment safety
• Industry-leading short circuit ratings
• An Ingress Protection safety rating of at least IP2X (‘finger safe’) and, if possible, options for IP3X (‘tool safe’)

Also, look for a busway system that gives you multiple ground path (earthing) options:

• Standard (protective) ground system – The busway’s aluminum housing provides the system’s ground conduction.
• Isolated ground system – The ground conductor and the housing ground are isolated from each other in all components. (This can be useful for protecting certain types of IT loads.)
• Dedicated ground system – The ground conductor and housing ground are bonded together at the end power feed.

Joints

A joint provides a connection between adjacent busway sections, or between a straight busway and an elbow or tee section. Different busway providers use different types of joints. But you should look for vendors that utilise the most reliable kind of joint – a compression-fit joint.

The housing couplers in the joints carry ground conduction through the aluminium housing from busway section to section. It’s therefore important to find a busway solution with reliable, well-designed joints in order to properly maintain the ground conduction system.

The problems of bolted and male/female joints

In selecting a busway system, you should avoid solutions where busway sections utilise bolted joints, which are less reliable than a compression-fit joint. In a bolted joint, bolts are used to press flat busbars together. Over time, the bolts can loosen, again resulting in a poor electrical connection. In a worst-case scenario, the joint can heat up to the burning point and potentially cause a fire in the data centre.

Bolted joints must frequently be checked via thermal imaging and re-torqued in order to maintain busway joint integrity. This adds to maintenance troubles and costs, especially in large data centres where thousands of bolted joints must be continuously serviced.

You should also avoid male and female joint couplings, which are easy to install incorrectly. The two busway sections must be perfectly aligned with each other and a misaligned coupling can result in a poor electrical connection between sections.

Plug-in units

The plug-in units (a.k.a. tap boxes) distribute the branch circuit power load from the busways to the servers, racks or other equipment. Plug-in units can be easily added or removed to the busway units as needed.

Safety of plug-in units is a primary concern, especially for facility engineers who often need to install tap boxes on live busways. At the most basic level, every plug-in unit from any vendor will have a grounding tab or device, which automatically grounds the unit prior to the electrical connection of the conductors into the busbars.

However, you should look for a busway solution with additional safety features:

First, the design of the busway itself contributes to safety where plug-in units are concerned. An asymmetrical U-shaped busbar design makes it impossible to install a plug-in unit incorrectly. This in turn makes it impossible to cross live phases or ground paths when installing the plug-in unit into a live busway.

You should look for a busway solution where the plug-in units come with optional safety accessories.

These might include:

‘Floor operable’ electrical connections – You can insert a plug-in unit into a live busway, step back to a safe distance and use a hook stick to turn the unit, which connects the paddle to the busbar and makes the electrical connection.

Breaker interlocks – A metal locking piece that prevents the unit from being installed or uninstalled while the breakers are on and the unit is under load.

Finger shrouds – A plastic ‘shroud’ cover that prevents the breaker switches on the unit from being turned off by accidental contact, i.e. during maintenance work on nearby server cabinets.

IR Windows – Infra-Red windows that allow for scanning of the plug-in unit’s internal power connections without performing hazardous work around live conductors.

Power monitoring

Today, many data centre owners do power monitoring at the PDU and rack PDU level. But this is not enough. For a more complete package of data, and to ensure the reliability and safety of your entire power distribution system, you should look for a busway solution that allows you to do critical power monitoring at various points along your busway runs.

A power monitoring system should have the ability to send out pre-set alarms in the event of a failure or emergency. For example, if a busway end feed rises to within 10 degrees of an unsafe temperature (i.e. ~85°C), the power monitoring system should have the ability to send an automatic email alert, or to provide that data to your BMS or DCIM, to warn you that a cable installation is potentially overheating and may cause a fire.

The monitoring system should also offer breaker-position sensing, which allows you to monitor whether plug-in units are operating correctly. Again, the system should allow you to pre-set alarms, so if, for example, a plug-in unit suddenly shuts off, you will receive an automatic email alert, indicating that a server rack may have overheated and triggered the breaker.

Conclusion

For data centre owners, CSEs and others who are seeking power delivery solutions, the ultimate goal in selecting a busway system should be peace of mind. You want the certainty and confidence that your power distribution system will always be able to deliver the power you need to your servers, racks or equipment.

A reliable busway system is not just a power solution. It provides a competitive advantage, allowing your data centre or other facility to stay operational. This ensures that your company will always be productive and able to deliver products or services to your customers.

At the same time, it is essential to select a busway system that will guarantee the safety of your workers, with the flexibility to adapt to the layout and changing power needs of your facility. If you evaluate the elements of a busway system based on these three qualities – reliability, flexibility and safety – and look for an experienced and highly-qualified provider who can also be a reliable business partner, you’ll be able to choose a busway solution that will effectively serve your power distribution needs over the long run.

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