How does one define when an Arc Flash Hazard exists?
According to NFPA 70E 2009, an Arc hazard is defined as, "A dangerous condition associated with the possible release of energy caused by an electric arc".
In FPN #1 it goes on to define it more with, "An arc flash hazard may exist when energized electrical conductors or circuit parts are exposed or when they are within equipment in a guarded or enclosed condition, provided a person is interacting with the equipment in such a manner that could cause an electric arc. Under normal operating conditions, enclosed energized equipment that has been properly installed and maintained is not likely to pose an arc flash hazard".
Then under section 110.7 (F) the document describes creating a Hazard/Risk evaluation program similar to that in appendix F.
Under 130.7(9) FPN #1, I read, "The work tasks and protective equipment identified in Table 130.7(C)(9) were identified by a task group and the protective clothing and equipment selected was based on the collective experience of the task group. The protective clothing and equipment is generally based on determination of estimated exposure levels. In several cases where the risk of an arc flash incident is considered low, very low, or extremely low by the task group, the hazard/risk category number has been reduced by 1, 2, or 3 numbers, respectively. The collective experience of the task group is that in most cases closed doors do not provide enough protection to eliminate the need for PPE for instances where the state of the equipment is known to readily change (e.g., doors open or closed, rack in or rack out). The premise used by the Task Group is considered to be reasonable, based on the consensus judgment of the full NFPA 70E Technical Committee."
Is the intent here not to look at an Arc Flash boundary strictly from a black and white perspective meaning that when you are within the Arc Flash boundary you must be appropriately attired in the correct level of Arc Flash PPE? This is the way we have implemented our program today and I am not sure this perspective is correct.
If, for example, we as the qualified personnel are opening a device for visual inspection by an unqualified individual, is the PPE only required to open the device and all other tasks that do not disturb the device and do not contact the device are not required to have this same level of PPE?
Another example: We have draw-out substation circuit breakers with trip units installed that require the qualified person to open the outer door to access the trip unit. This person must where the appropriate level of PPE to open the door but if another qualified person is to adjust the trip unit, does that person also need the same level of PPE. He is not close to any accessible conductors or parts but they are exposed in the cubicle?
Should each of these tasks be evaluated for the level of intrusiveness and risk similar to what is shown in the Appendix F? This seems contrary to the NFPA document and IEEE-1584 but it does appear to be what the 2009 update is leaning toward.
According to NFPA 70E 2009, an Arc hazard is defined as, "A dangerous condition associated with the possible release of energy caused by an electric arc".
In FPN #1 it goes on to define it more with, "An arc flash hazard may exist when energized electrical conductors or circuit parts are exposed or when they are within equipment in a guarded or enclosed condition, provided a person is interacting with the equipment in such a manner that could cause an electric arc. Under normal operating conditions, enclosed energized equipment that has been properly installed and maintained is not likely to pose an arc flash hazard".
Then under section 110.7 (F) the document describes creating a Hazard/Risk evaluation program similar to that in appendix F.
Under 130.7(9) FPN #1, I read, "The work tasks and protective equipment identified in Table 130.7(C)(9) were identified by a task group and the protective clothing and equipment selected was based on the collective experience of the task group. The protective clothing and equipment is generally based on determination of estimated exposure levels. In several cases where the risk of an arc flash incident is considered low, very low, or extremely low by the task group, the hazard/risk category number has been reduced by 1, 2, or 3 numbers, respectively. The collective experience of the task group is that in most cases closed doors do not provide enough protection to eliminate the need for PPE for instances where the state of the equipment is known to readily change (e.g., doors open or closed, rack in or rack out). The premise used by the Task Group is considered to be reasonable, based on the consensus judgment of the full NFPA 70E Technical Committee."
Is the intent here not to look at an Arc Flash boundary strictly from a black and white perspective meaning that when you are within the Arc Flash boundary you must be appropriately attired in the correct level of Arc Flash PPE? This is the way we have implemented our program today and I am not sure this perspective is correct.
If, for example, we as the qualified personnel are opening a device for visual inspection by an unqualified individual, is the PPE only required to open the device and all other tasks that do not disturb the device and do not contact the device are not required to have this same level of PPE?
Another example: We have draw-out substation circuit breakers with trip units installed that require the qualified person to open the outer door to access the trip unit. This person must where the appropriate level of PPE to open the door but if another qualified person is to adjust the trip unit, does that person also need the same level of PPE. He is not close to any accessible conductors or parts but they are exposed in the cubicle?
Should each of these tasks be evaluated for the level of intrusiveness and risk similar to what is shown in the Appendix F? This seems contrary to the NFPA document and IEEE-1584 but it does appear to be what the 2009 update is leaning toward.
