Beware Data Center Danger Zones

It’s crucial to understand arc-flash hazards and take steps to mitigate risks.

Electrical systems are the foundation of data-center operations. The very nature of these business-critical facilities makes them potential danger zones for those involved in building, maintaining, and modifying them.

Working around data-center power systems can be dangerous due to their complexity, including redundant circuitry and uninterruptible power supplies (UPS) that can switch without warning in just a few milliseconds. Adding to the danger, a data center’s electrical equipment is sometimes serviced while energized. With the growing trend toward larger power capacities, data-center systems may also have a high level of available fault current that further increases risk to personnel, especially if they are unaware of potential hazards and how to mitigate them.

Arc flash is one of those hazards—one with serious consequences. The Institute for Electrical and Electronics Engineers (IEEE, ieee.org, New York) reports that 2,000 workers are admitted to burn centers each year for extensive injuries caused by arc flash, which is defined by the National Fire Protection Association (NFPA, nfpa.org, Quincy, MA) as an electric current that passes through air when insulation or isolation between electrified conductors is not sufficient to withstand the applied voltage.

Arc flash produces temperatures as high as 35,000 F. That’s four times hotter than the surface of the sun. The resulting blast is similar to an explosion, creating enough force to throw a worker’s body across a room. Even someone standing more than 10 ft. away from the fault source could be severely burned by such a blast.

Beyond the risk of personal injury and death, an arc-flash event can also lead to:

• business disruption
• damage to equipment and facilities
• legal liability
• increased insurance premiums
• hefty regulatory fines.

Understanding relevant standards

Arc-flash concerns were first publicized in the early 1980s with the release of a paper by Ralph Lee titled, “The Other Electrical Hazard: Electric Arc Blast Burns.” Similar studies illustrated that too many people were suffering injuries due to arc-flash incidents.

Early adopters subsequently took steps to establish the first set of practices designed to better protect employees and electrical contractors. Soon after, others recognized the need for additional protection against arc-flash hazards and new requirements were created.

Today, the Occupational Health and Safety Administration (OSHA, osha.gov, Washington) sets out the legal requirement for employers to provide a safe work environment, and its regulations are enforceable under federal law. NFPA serves as the world’s leading advocate of fire protection and has published more than 300 consensus codes and standards.

Together, OSHA and NFPA are working to ensure safe working conditions. Although OSHA outlines general requirements, in many cases it doesn’t explain how to meet them. This is left to national consensus standards.

There are essentially four main regulations governing arc flash:

OSHA Standards 29 CFR, Part 1910: Occupational Safety and Health Standards, subpart S (electrical) standard number 1910.333 specifically addresses standards for work practices and references NFPA 70E.

NFPA Standard 70: National Electrical Code (NEC) contains requirements for warning labels.

NFPA 70E: Standard for Electrical Safety in the Workplace provides guidance on implementing appropriate work practices that are required to safeguard workers from injury while working on or near exposed electrical conductors or circuit parts that are or become energized.

IEEE 1584: Guide for Performing Arc Flash Hazard Calculations provides a method of calculating the incident energy to define the safe working distance and aid in selection of overcurrent protective devices and personal protective equipment (PPE).

Ensuring safety and compliance

In 2016, three of OSHA’s 10 most frequently cited violations were related to electrical-system practices and procedures. For data-center owners and operators, the first step in avoiding such citations is to audit their sites’ safety policies and programs. These types of audits should take place every three years and be documented, noting any deficiencies that need to be addressed.

NFPA 70E requires employers to develop, implement, and document an overall safety program. The program must be designed to train employees and instill an awareness of electrical hazards. It should identify hazard/risk evaluation procedures, required tools and PPE, electrically safe work procedures, and risk-mitigation strategies.

Mitigation of arc flash and related hazards has a lot to do with training. The root cause of many arc-flash accidents is insufficient training. That situation, in turn, results in failure to follow appropriate procedures or take necessary safety precautions on the job. The following strategies can help facilities comply with NFPA 70E (which is the best way to ensure compliance with OSHA codes and regulations):

Qualify workers: OSHA and NFPA recognize the importance of ensuring worker qualification. To be qualified to work on or around electrical equipment, a worker must demonstrate the ability—not simply familiarity—to use special precautionary techniques and PPE. This includes arc-flash suits, insulating and shielding materials, and insulated tools and test equipment. Qualified persons who perform maintenance on electrical equipment and installations must also be trained and familiar with the specific maintenance and test procedures required.

Train all at-risk workers: Employees who work around (not just on) energized electrical equipment must be safety trained, preferably through an instructor-led course, as opposed to web-based training. Qualified electrical workers permitted to work within the limited approach boundary of exposed energized electrical conductors and circuit parts operating at 50 V or more must be trained to understand and observe minimum approach distances to exposed parts.                                                                          

Retraining must occur at least every three years, whenever new procedures or practices are introduced, or when an audit indicates a need for additional training. All employee training must be documented and training programs audited every three years.

Evaluate workers annually: Data centers must conduct annual inspections to ensure each employee is complying with safety-related work practices. The annual audit requirement applies to work involving electrical equipment.

Beyond worker training, there are additional work practices that help mitigate arc-flash dangers:

Maintain a single-line diagram. A data-center manager must maintain an accurate, up-to-date, and legible single-line diagram of the operation. Building-maintenance personnel, electricians, and engineers rely on a single-line diagram as a map to guide them around the electrical system, making this schematic essential for documenting, troubleshooting, and communicating information about the system.

Maintain electrical equipment. NFPA 70E specifies that the equipment owner is responsible for electrical-equipment maintenance and documentation of that maintenance. To reduce the risk of failure and the subsequent exposure of employees to electrical hazards, data-center managers must conduct maintenance in accordance with manufacturer instructions or industry consensus standards. Industry consensus standards include American National Standards Institute/InterNational Electrical Testing Association Standard for Maintenance Testing Specifications (ANSI/NETA MTS) and NFPA 70B Recommended Practice for Electrical Equipment Maintenance.

Determine protection requirements. A required arc-flash analysis identifies the presence and location of potential hazards and provides information to help personnel select proper PPE. Note that section 110.1 G of NFPA 70E states that elimination, substitution, engineering controls, awareness, and administrative controls are all preferred over use of PPE. However, because of the nature of data centers, use of PPE is necessary. Additionally, NFPA 70E dictates that the arc-flash boundary distance must be calculated for all locations where the voltage exceeds 50 V and where there is a possibility of performing energized work such as maintenance, diagnostics, and testing.

Apply hazard labels. NEC and NFPA 70E require data-center owners to apply an arc-flash hazard warning or label to electrical equipment in the field including switchboards, switchgear, panel boards, industrial control panels, meter socket enclosures, and motor-control panels that are likely to require maintenance while energized.

Arc-flash-hazard labels must include information on nominal system voltage, arc-flash boundary, minimum arc rating of clothing, site-specific level of PPE, and one, but not both, of the following:

• available incident energy and the corresponding working distance (if the arc-flash boundary was calculated through engineering analysis)

• arc-flash PPE category in the NFPA 70E tables (if the table method was used to calculate arc-flash boundary).

Perform a battery-related risk assessment. Prior to doing any work on a battery system, a risk assessment must be performed to identify the chemical, electrical shock, and arc-flash hazards; and assess the risks associated with the tasks to be performed.

Keep in mind that if a data center is noncompliant with applicable standards, it jeopardizes the overall safety of its workers and potentially faces other costly consequences. EP

Information in this article was provided by Steve Park, P.E., technical services manager of Electrical Reliability Services at Vertiv (vertivco.com, Columbus, OH), which was formerly known as Emerson Network Power. Park received his Bachelor’s and Master’s degrees in electrical engineering from Purdue Univ., West Lafayette, IN, and an MBA from Indiana Wesleyan Univ., Marion, IN. He has been a registered professional engineer since 1992. For more information on issues of electrical safety and data-center management, email steve.park@vertivco.com.