The failure to protect the employees against injury or death from Arc Flash can put them out of business. Failing to keep up with the latest Arc Flash safety standards and guidelines can cost time and money.
Electricity is recognized as a serious workplace hazard where OSHA regulations and NFPA 70E standards exist to protect personnel against arc flash and shock hazards.
arc flash
Arc Flash is the sudden release of energy when a fault or short circuit occurs between the air gap
An “Arc Flash” is the sudden release of energy when a fault or short circuit occurs between the air gap of energized electrical conductors. It can set fire to clothing, severely burn human skin, liquefy and vaporize metal parts, cause explosive pressure and sound waves, cause blindness from the intense light flash, rupture eardrums, spray molten metal throughout the vicinity, and eject personnel across a room.
If those events don’t kill the personnel, the solid metal debris and other loose objects turned into shrapnel and deadly projectiles by the explosion might.
three applicable standards to ensure safety
They will reduce the probability of injuring the employees and facing legal action, including OSHA penalties, by following these three principle standards and staying up to date with them.
- National Electrical Code (NEC) – The benchmark adopted by all 50 states for safe electrical design, installation, and inspection to protect people and property from electrical hazards.
- National Fire Protection Association (NFPA) 70E – The standard for electrical safety in the workplace and for employee safety when interacting with energized electrical equipment.
- Institute of Electrical and Electronics Engineers (IEEE) 1584 – The guide for mathematical calculations to determine the arc flash boundary and the arc flash incident energy to which workers could be exposed when interacting with electrical equipment.
Here is a brief summary of what they need to know about the three major standards of NEC, NFPA 70E, and IEEE 1584.
National Electrical Code (NEC) requirements for 2020
All electrical installations need to comply with NEC for arc flash hazards. The latest NEC (2020 Edition) mandates:
- All electrical equipment that is likely to require examination, adjustment, servicing, or maintenance must be marked to warn personnel of potential arc flash hazards.
- Service electrical equipment rated 1200A or more must also be marked to indicate nominal system voltage, available short circuit current, and the total fault clearing time of the breaker/fuse.
- Fuses rated 1200A and larger must have a total clearing time of 0.07 seconds or less for the corresponding arc flash current.
- Arc flash energy reduction capabilities must be implemented using an approved/listed method for circuit breakers rated 1200A and larger.
National Fire Protection Association (NFPA) 70E requirements for 2021
NFPA 70E provides safety guidelines and standards that work in conjunction with the NEC. The 2021 Edition recommends the following:
- Implement written procedures for performing work involving electrical shock and arc flash hazards.
- Establishing electrically safe working conditions must be the primary strategy to protect personnel against electrical hazards. This includes de-energization of the equipment, isolation of all live power sources, and establishing a lockout/tagout procedure.
- Obtain proper justification and execute an energized work permit in the event that energized electrical equipment becomes absolutely necessary. A mere inconvenience associated with an undesired power outage to occupants or a facility is not recognized as a valid justification to perform live work.
- Determine the likelihood of an arc flash occurrence and identify an arc flash risk assessment method. By using the incident energy analysis method, the estimated arc flash boundary and arc flash incident energy can be determined. These results can then be used for the selection of appropriate arc-rated Personnel Protective Equipment (PPE).
- Affix labeling on electrical equipment that is likely to require examination, adjustment, servicing, or maintenance. When using the incident energy analysis method, the following minimum label parameters can be listed: nominal system voltage, arc flash boundary, and arc flash incident energy. Arc flash labeling also needs to be updated every 5 years or whenever a major electrical system upgrade takes place.
IEEE 1584 requirements for 2018
IEEE 1584 provides a guideline for calculating both the estimated arc flash boundary and arc flash incident energy that is referenced in NFPA 70E. For arc flash calculations, the 2018 Edition requires careful consideration of the following parameters:
- Electrical system: The IEEE guideline applies to AC voltages that range between 208 V and 15 kV, where the system frequency is either 50 Hz or 60 Hz.
- Bolted fault current: The three-phase bolted fault current at given equipment should be determined in advance via a short circuit study in order to determine the corresponding arcing fault current.
- Fault clearing time: The fault clearing time is the total duration that it takes for a circuit breaker (or fuse) to interrupt and clear the arcing fault, which is determined by the selection of a protection device and its adjustment via a coordination study.
- Conductor (bus) gaps: The conductor gap pertains to the distance of separation between energized conductors or buses where an electrical arc might be established.
- Working distance: The working distance pertains to the distance between the worker and the source of the arc flash.
- Enclosure size: This pertains to the overall dimensions of the electrical equipment enclosure or cubicle where an arc flash event can occur.
- Electrode configuration: This pertains to the physical arrangement of the equipment bus which can include horizontal conductors in a box (HCB), vertical conductors in a box (VCB), vertical conductors in a box with insulating barriers (VCBB), horizontal conductors in the open air (HOA), or vertical conductors in the open air (VOA).
