Overview – In a matter of 60 seconds, today’s Internet handles hundreds of new websites going up, thousands of uploaded photos, millions of searches, and hundreds of millions of emails being sent. This demand for bandwidth is only increasing, and with it, so is the demand for power. By Mark A. Swift – Director of Marketing for Universal Electric Corporation (STARLINE); Timothy Crnko – Manager Technical Services for Eaton’s Bussmann Business; and Calvin Nicholson – Senior Director of Software and Firmware for Server Technology.

FACILITIES NEED TO BE LARGER to accommodate for more servers, and facilities managers need to be able to quickly address this constant need for additional capacity. In order to support the extra elements required, worldwide IT spending on servers, power and cooling, and management/administration has rapidly increased over the past decade. But other than just an increase in costs, the need for higher power densities poses additional challenges. It requires more power to the racks and can result in higher distribution voltages, larger ampacity circuits, and higher available fault currents.

This evolution requires specifiers of the white space electrical distribution equipment and power distribution units (PDUs) to assess their needs and select equipment with overcurrent protection that ensures reliable power delivery while complying with the safety requirements of the National Electrical Code (NEC) and Occupational Safety and Health Administration (OSHA) safe work practices.

Typically, the demand for 415 V power applications are driven by the desire for greater power efficiencies within the data centre. Servers run more efficiently at higher voltages and the power distribution system is more efficient converting the incoming power down to 415/240V rather than 208/120V AC.

More power density means a more prevalent threat of higher available fault currents. The result is the analysis and selection of the overcurrent protection scheme is more demanding to ensure proper interrupting rating, selective coordination, and arc flash reduction. This is especially prevalent with higher-voltage distribution system architectures like 415/240V AC. However, a holistic fused architecture for your data center white space power electrical distribution provides an easy means to provide the level of protection needed for this high reliability, high power density application.

Circuit protection

In a world evolving to more power, there is also a pressing need for overcurrent protective devices with higher interrupting ratings (IR) without excessive physical size or cost. Both the NEC and OSHA require circuit breakers and fuses to have interrupting ratings equal to or greater than the available short-circuit current at their lineside terminals. Bussmann Low-Peak LPJ(amp)SP fuses (end feed) and compact CUBEFuses (plug-in unit) that are used in data centre busway systems have interrupting ratings of either 200 kA or 300 KA at 600V AC or less, which is much higher than the typical 10 KA to 22 KA circuit breaker used in busway plug-ins.

Bussmann SC 20 fuses that are used in PDUs have interrupting ratings of 100 kA at 600V AC or less, which is substantially higher than the usual 5 kA or 10 kA interrupting rating circuit breakers used in PDUs. With Bussmann fuses it is easy to meet the interrupting rating requirement and offer the additional benefit of current-limitation to effectively provide excellent equipment short-circuit protection and mitigate arc-flash incident energy.

During one test demonstration, a current-limiting fuse reduced the mechanical force 96% and reduced the thermal energy 99% compared to a non-current-limiting overcurrent protective device. This means that under fault conditions within the current-limiting range of a fuse, the fault current duration and magnitude can be significantly reduced. This performance can minimize equipment damage and can substantially reduce the arc flash hazard.

“In order to properly accommodate higher power densities, key power system considerations include interrupting rating (IR), short-circuit current rating (SCCR), current-limitation, selective coordination, and arc flash mitigation.” states Tim Crnko, manager of electrical technical services for Eaton’s Bussmann Business. Bussmann Low-Peak LPJ(amp) SP fuses, compact CUBEFuses integral with the Compact Circuit Protector switch (CCP), and SC fuses effectively address these key power system considerations. Bussmann fuses, when properly chosen, also incorporate selective coordination, so only the closest upstream overcurrent protective device (OCPD) opens from an overcurrent condition. This preventative measure eliminates unnecessary outages caused by cascading of OCPDs, and ensures better system reliability. Including fusing as part of your data centre power distribution design will incorporate many of these benefits.

Track Busway

Another key component in addressing data centre overcurrent protection challenges is, obviously, your power distribution system. Due to benefits such as faster installation times, reduced facility construction costs, and flexible power access, STARLINE Track Busway has become the supplier of choice for the mission critical environment.

Combined with Bussmann fuses, the STARLINE system becomes a powerful solution for combatting downtime, increasing overall safety, and complying with the stringent NEC and OSHA requirements.

Data centre managers and designers do not have to be concerned with the level of short circuit currents, and the rating of the plug-in can simply be changed by installing a new fuse without removing the plug-in from the busway. If a fault occurs, selective coordination ensures an outage is limited only to the portion of the circuit that has the problem, and there are no loads that incur unnecessary power outages. Plus, more power can be added by simply adding another plug-in unit whenever expanded capacity is needed.

“All components of the STARLINE Track Busway system are easy to install, expand, relocate, reconfigure, and customize- which is why it’s become the industry standard for data centres,” says Mark Swift, director of marketing for STARLINE. “In addition, the fuse in the plug-in unit can easily be serviced without opening the enclosure. Collaborating with both Bussmann and Server Technology has allowed us to put together a holistic solution to help the mission critical environment with overcurrent protection challenges.”

The STARLINE Track Busway system with Bussmann fuses incorporated in both the end feeds and plug-in units was successfully tested and passed, achieving a 200kA short circuit rating with a fully coordinated design.


Recent advancements in PDU technology have led to Server Technology’s launch of the PRO2 family of products. A key PRO2 feature is the redundantly powered hot swappable network card. This ensures uptime and availability of the network interface even if power is lost to the Master PDU. In the unlikely event the network card does fail, it can be hot-swapped under power without any additional configuration or other changes.

“The new PRO2 architecture is ideal any place where reliability and uptime are important, particularly in high density, high-temperature, and high-security applications,” said Calvin Nicholson senior director of software and firmware development.

The Server Technology fused PDU offering uses fuses from the same family as those incorporated in the STARLINE design. That gives you the additional benefit of having the in-rack power distribution also fully coordinated with the upstream power distribution equipment- delivering a safer scenario for both your workforce and ensuring uptime of critical equipment.


The demand for higher density data centres is resulting in the need for the specifiers of both busway systems and the PDU systems to assess the more demanding needs of these systems relative to overcurrent protection. With higher power densities, reliability is even more important. Utilizing higher voltages with often higher ampacity circuits results in higher available fault currents. Modern high interrupting rating, current-limiting Bussmann fuses integral with the STARLINE Track Busway system and the Server Technology PDUs are a simple, easy means to ensure proper ratings, selective coordination, and safe work practices.

Rahi is a Global IT Solutions Provider. We are uniquely capable of combining data center, IT and audio/video solutions to create an integrated environment that drives efficiencies, enhances customer service and creates competitive advantages. We offer a full suite of products in physical infrastructure, storage, compute, networking, power and cooling, and audio / video. In addition, Rahi offers professional and managed services to aid customers in logistics, delivery, set-up, and ongoing support of their technology solutions.

About Rahi

Rahi is a subsidiary of Wesco Distribution, a Fortune 200 Company with operations in 50+ countries and annual revenues over USD 19B. Rahi delivers comprehensive data centre solutions for global enterprises, hyperscalers, and multi-tenant data centres. Rahi provides IOR, local currency billing, and RMA services, enabling businesses to operate efficiently anywhere.
Since being acquired in Nov. 2022, Rahi’s global presence and analytical expertise help clients achieve their business and IT requirements.

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