Arc Flash Safety in 400V Data Centers Strategies for protecting employees from underappreciated yet potentially deadly hazards By Dave G. Loucks Manager, Power Solutions and Advanced Systems Eaton

The rise of the 400V data center In the U.S., utilities typically deliver power at 480V. Most U.S. data centers, however, operate at 120V/208V. As a result, they must use a series of mechanisms to “transform” or “step down” power from the 480V at which it’s received to the 120V at which it’s consumed by servers and other infrastructure devices. Unfortunately, a small amount of energy gets lost as waste during each of those steps. One way to reduce such waste is to operate the data center at 400V, as organizations in most countries around the world already do. In a 400V data center, fewer voltage...

IEEE 1584-2002: Created by the Institute of Electrical and Electronics Engineers (IEEE), one of the world’s most respected technical professional associations, IEEE 1584-2002 offers guidance on measuring the incident energy associated with arc flash events, as well as recommendations on how much PPE workers require based on those measurements. For more information, visit http://ieee.org and search for “1584-2002”. NFPA 70E: Produced by the National Fire Protection Association, a non-profit organization dedicated to fire, electrical, building and life safety, NFPA 70E defines thresholds for appropriate...

Figure 1. Creating multiple power paths all the way from utility mains to UPSs to IT equipment (ITE) can improve both reliability and safety. However, companies can temporarily use parallel redundant power architectures to promote safety rather than reliability, by manually de-energizing a power path before repairing or administering the IT equipment it supports. Though such a move briefly increases the risk of downtime, it also reduces the risk of arc flashrelated injuries. For most businesses in most situations, that’s a tradeoff worth making. 5. Use circuit breakers with fuses Generally speaking,...

Be sure, however, to look for arc flash reduction maintenance systems that operate even faster than the circuit breaker’s normal instantaneous clearing time. Such products include dedicated high-speed analog tripping circuitry that bypasses the circuit breaker trip unit. Modern electronic trip units use microprocessors to calculate currents and decide when to trip. The time delays introduced by executing this program code (not to mention boot-up time if the breaker is closed into a fault and the microprocessor is initially powered up), are eliminated by the analog bypass circuit. Zone selective...

Predictive maintenance systems: Deteriorating insulation is the leading cause of arc-producing electrical failures. Identifying and repairing compromised insulation before it fails can help avert arc flash explosions. Predictive maintenance systems provide early warning of insulation failure in medium-voltage switchgear, substations, generators, transformers and motors. Remote monitoring, control and diagnostics software: With the help of power management systems, technicians can perform many administrative tasks remotely, rather than expose themselves to potential arc flash events. Power management...

Conclusion Long common elsewhere in the world, 400V data centers are slowly gaining popularity in the U.S., at least partly because they eliminate 480V to 120V transformers and thus offer superior energy efficiency. Yet operating a data center at 400V poses arc flash risks far more severe than those found in a 120V data center. To protect their employees from disabling and even lethal injuries, organizations contemplating a move to 400V must carefully study the potential hazards and supply their people and facilities with appropriate PPE, circuit protective devices and training. By doing so,...