“(Are) operating breakers – opened/closed considered an arc flash exposure even if the hinged cover is on?”
NFPA’s 70E addresses that question in the “Informational Note No. 1 under the definition of “Arc Flash Hazard”:
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. (Underlining is mine) Under normal operating conditions, enclosed energized equipment that has been properly installed and maintained is not likely to pose an arc flash hazard.
The two key parts of this statement are:
1. Whenever a person interacts with electrical equipment, such as an opening/closing operation, even though the door is closed or the cover is on, an arc flash hazard may exist.
2. If the equipment has been properly installed, according to the National Electric Code, and properly maintained, using such resources as NFPA’s Standard 70B and the International Electrical Testing Association’s Standard for Maintenance Testing Specifications, an arc flash hazard is not likely to occur.
A person needs to take into account the age of the equipment, the design of the equipment, as well as its installed and maintained condition in order to determine if there is an arc flash hazard when open or closing a circuit breaker.
A similar response was given in an OSHA letter of interpretation: