NFPA 70E Table 130.5(C): Likelihood of Arc Flash Incident

NFPA 70E Table 130.5(C) is applicable to both the PPE Categories Method (Tables Method) and the Incident Energy Analysis Method of arc flash risk assessment. The first column lists types of tasks. The second column describes the condition of the equipment, which effects the likelihood of an arc flash incident. The third column says if there is a likelihood of an arc flash incident (“Yes/No”).

Both AC and DC tasks are listed in the table. See the note at the end of table that describes what is considered a "Normal" equipment condition. If any of the criteria are not met, the equipment condition would be considered "Abnormal."

This table does not determine if arc flash PPE is necessary. Rather, it's purpose it to aid in determining the likelihood of an arc flash incident occurring. If a likelihood exists, other hazard control options must be used first. PPE should only be used after all other means of employee protection have been exhausted. PPE is considered the least effective control for employee protection and should not be the first or only hazard control used.

Equipment condition is considered to be “normal” if all of the following circumstances apply:

1. The equipment is properly installed in accordance with the manufacturer’s recommendations and applicable industry codes and standards.
2. The equipment is properly maintained in accordance with the manufacturer's recommendations and applicable industry codes and standards.
3. The equipment is used in accordance with instructions included in the listing and labeling and in accordance with manufacturer’s instructions.
4. Equipment doors are closed and secured.
5. Equipment covers are in place and secured.
6. There is no evidence of impending failure such as arcing, overheating, loose or bound equipment parts, visible damage, or deterioration.

*As defined in this standard, the two components of risk are the likelihood of occurrence of injury or damage to health and the severity of injury or damage to health that results from a hazard. Risk assessment is an overall process that involves estimating both the likelihood of occurrence and severity to determine if additional protective measures are required. The estimate of the likelihood of occurrence contained in this table does not cover every possible condition or situation, nor does it address severity of injury or damage to health. Where this table identifies “No” as an estimate of likelihood of occurrence, it means that an arc flash incident is not likely to occur. Where this table identifies “Yes” as an estimate of likelihood of occurrence, it means that additional protective measures are required to be selected and implemented according to the hierarchy of risk control identified in NFPA 70E 110.1(H).

Informational Notes No. 1-6

Informational Note No. 1: An example of a standard that provides information for arc-resistant switchgear referred to in Table 130.5(C) is IEEE C37.20.7, Guide for Testing Metal-Enclosed Switchgear Rated Up to 38 kV for Internal Arcing Faults.

Informational Note No. 2: Improper or inadequate maintenance can result in increased fault clearing time of the overcurrent protective device, thus increasing the incident energy. Where equipment is not properly installed or maintained, PPE selection based on incident energy analysis or the PPE category method might not provide adequate protection from arc flash hazards.

Informational Note No. 3: Both larger and smaller available fault currents could result in higher incident energy. If the available fault current increases without a decrease in the fault clearing time of the overcurrent protective device, the incident energy will increase. If the available fault current deceases, resulting in a longer fault current clearing time for the overcurrent protective device, incident energy could also increase.

Informational Note No. 4: The occurrence of an arcing fault inside an enclosure produces a variety of physical phenomena very different from a bolted fault. For example, the arc energy resulting from an arc developed in the air will cause a sudden pressure increase and localized overheating. Equipment and design practices are available to minimize the energy levels and the number of procedures that could expose an employee to high levels of incident energy. Proven designs such as arc-resistant switchgear, remote racking (insertion or removal), remote opening and closing of switching devices, high-resistance grounding of a low-voltage and 5000-volt (nominal) systems, current limitation, and specification of covered bus or covered conductors within equipment are available to reduce the risk associated with an arc flash incident. See Informative O for safety-related design requirements.

Informational Note No. 5: For additional direction for performing maintenance on overcurrent protective devices, see Chapter 2, Safety-Related Maintenance Requirements.

Informational Note No. 6: See IEEE 1584, Guide for Performing Arc Flash Calculations, for more information regarding incident energy and the arc flash boundary for three-phase systems.