Data Center Arc Flash Safety - Answers
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Here are the answers!
1. Which of the following can initiate an electrical arc?
- d. All of the above
Explanation: Some arcs are caused by human error including dropped tools, accidental contact with electrical systems, and improper work procedures. Another common cause of an arc is insulation failure. Build-up of dust, contamination, and corrosion on insulating surfaces can provide a path for current flow. Sparks created during racking of breakers, replacement of fuses, and closing into faulted lines can also produce an arc. Birds, rodents, and other animals can inadvertently bridge the space between conductors or cause leads to slap together, creating an arcing fault.
2. According to a collaborative research project between the Institute of Electrical and Electronics Engineers (IEEE) and the National Fire Protection Association (NFPA), approximately how many workers are admitted to burn centers each year for treatment of extended injury caused by arc flash?
- c. 2,000
Explanation: It’s clear that electrical accidents in the data center can have severe and often devastating consequences. Arcing from an electrical fault can produce temperatures hotter than the surface of the sun, creating an incredibly hot blast with force similar to an explosion—enough to throw a worker’s body across the room. Beyond the risk of personal injury and death, arc flashes can also lead to business disruption, costly damage to equipment and facilities, legal liability, increased insurance premiums, and hefty regulatory fines.
3. To be “qualified” to work on or around electrical equipment according to NFPA 70E: Standard for Electrical Safety in the Workplace, individuals must demonstrate the ability to use which of the following:
- d. All of the above
Explanation: Both OSHA and NFPA recognize the importance of determining a worker’s qualifications. Individuals must be trained and knowledgeable in the construction and operation of equipment or specific work methods, and be trained to recognize and avoid electrical hazards that might be present with respect to that equipment or method. The latest version of NFPA 70E states that workers must also demonstrate skills and knowledge related to the construction and operation of electrical equipment and installations, rather than just being familiar with them.
4. Which of the following is NOT contained in the risk assessment definition of NFPA 70E:
- a. Process that identifies the prohibited approach boundary
Explanation: The shock protection boundary identified as the “prohibited approach boundary” was removed from NFPA 70E in 2015 and has nothing to do with a risk assessment. In the latest version of the standard, “risk” primarily refers to the chance or probability that the identified hazard could result in physical harm to the worker, or the unqualified or unprotected persons nearby. The risk assessment process is the key to determining the necessity to use PPE.
5. Which of the following was NOT a change made as part of the 2015 NFPA 70E updates:
- d. Updates to the arc flash risk assessment are now only required every 10 years
Explanation:Requirements about the frequency for risk assessment updates were not changed in the 2015 version of NFPA 70E. An arc flash risk assessment should be updated when a major modification or renovation takes place and it should be reviewed periodically, not to exceed five years, to account for changes in the electrical distribution system (or regulatory guidance).
6. There is a legal requirement for a registered professional engineer to perform arc flash hazard analysis.
- b. False
Explanation: While having a registered PE perform hazard analysis isn’t a legal requirement, such expertise not only ensures compliance with the standards, it can also save lives since improper calculations can put workers in grave danger.
7. Arc flash labels only need to be updated following major changes to the electrical distribution system.
- b. False
Explanation: Section 130.5 of NFPA 70E says that labels need to be updated if the arc flash risk assessment shows that the labels are inaccurate. While arc flash labels should be updated upon major changes to the electrical distribution system, even small adjustments like replacing a fuse or circuit breakers, or changing trip units and protective relays can affect arc flash analysis and the resulting field label information. Ideally, a qualified engineering company should assist with an arc flash assessment and label review when any changes are made to the distribution system, or every five years at a minimum.
8. If a field label includes available incident energy and the corresponding working distance, which other piece of information is NOT required:
- c. Equipment’s arc flash PPE category as determined from NFPA 70E tables
Explanation: Required is available incident energy and the corresponding working distance, or the arc flash PPE category in Table 130.7(C)(15)(A)(b) or Table 130.7(C)(15)(B) for the equipment, but not both. The table method and the engineering assessment cannot be mutually applied to the same piece of equipment. Additionally, the table method can only be applied when specific requirements such as available fault current and clearing times are met—values typically not know unless an engineering study is performed.
9. After achieving a level of incident energy that is acceptable according to your company’s safety policy, it is safe to assume that system equipment will remain at or below that acceptable level.
- b. False
Explanation: There are many instances where the arc flash incident energy level can increase as you move deeper “downstream” or away from the supply point. This increase can occur due to decreased arcing current levels that fall below the instantaneous pickup of an overcurrent protective device. This creates a longer time delay before a fault is interrupted, which results in much higher incident energy levels.
10. Which of the following resources is best suited to provide a comprehensive arc flash solution?
- a. A qualified electrical engineering and services provider with data center expertise
Explanation: When engaging a service organization for an arc flash solution, it should not only have qualified electrical engineers, but it should also have in-depth industry knowledge along with extensive power system analysis experience. It is this expertise that allows for a thorough power system evaluation that is tailored to your specific infrastructure.
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