OSHA standards require a workplace free from exposure to electrical hazards. Electrical safety in the workplace is achieved through (1) adherence to applicable installation requirements in NFPA 70, the National Electrical Code; (2) the implementation of electrical safe work practices in NFPA 70E, the Standard for Electrical Safety in the Workplace; and (3) maintaining electrical equipment in accordance with NFPA 70B, the Recommended Practice for Electrical Equipment Maintenance. These documents represent a three-legged stool that supports electrical safety in the workplace. If we remove one of them, the stool falls, representing the failure of effective electrical safety in that workplace.
We often perform maintenance in our daily lives. For example, we understand the need to keep our vehicles in working order. We change the oil and check the brakes, transmission, headlights, brake lights and more without question. We accept these maintenance activities because we want our vehicles to be reliable and safe.
In the workplace, considering the condition of maintenance of electrical equipment is an essential component of a contractors’ electrical safety program. What is maintenance? The standard definition is “the process of maintaining or preserving something.” When applying this term to requirements in NFPA 70E, we are referring to electrical preventative maintenance. The maintenance of electrical equipment is the responsibility of the equipment owner.
Employers must make an assessment of electrical equipment status with respect to maintenance. In many cases, this can be determined through the common industry practice of applied test, maintenance or calibration decals. Most maintenance programs are initiated and continued for the purpose of reliability, because the owner does not want electrical equipment failure to interrupt their daily operations. Maintaining equipment for system reliability has a significant impact on electrical safety.
NFPA 70E contains requirements that mandate the user of the standard consider the maintenance of electrical equipment. NFPA 70E defines the condition of maintenance as the state of the electrical equipment considering the manufacturers’ instructions and recommendations, as well as applicable industry codes, standards and recommended practices. NFPA 70E contains requirements for employers with respect to maintenance when performing a shock or arc flash risk assessment. These are safety-driven requirements, not best practices designed to enhance system reliability.
Safety-related work practices include the verification of proper maintenance and installation. The required electrical safety program must include elements that describe how the employer will ensure that electrical equipment has been properly maintained before justified energized work is performed. These required elements must be part of the employer’s written shock and arc flash risk assessment procedures.
This is just one example of how an effective electrical safety program directs activity appropriate to the risk associated with electrical hazards. When estimating the likelihood and severity of a potential incident, shock and arc flash risk assessments require that design of the equipment, its operating condition and condition of maintenance be considered.
The arc flash risk assessment also requires you consider the overcurrent protection device (OCPD) and associated clearing time. Failure of any function in electrical equipment can introduce, increase the likelihood of and increase the potential severity of a shock or arc flash incident, so maintenance of OCPDs is extremely important.
The clearing time in an arcing event is directly proportional to the incident energy. The informational notes to Table 130.5(C) for the estimate of likelihood of an arc flash incident provide this information, explaining that improper or inadequate maintenance can result in increased fault clearing time of the OCPD, which will increase the incident energy.
It is imperative for the user of the standard to understand that where equipment, such as a low-voltage power circuit breaker, is not properly maintained, the personal protective equipment selection, based on an incident energy analysis or the arc-flash PPE category method, might not provide adequate protection from arc flash hazards. If an OCPD takes twice as long to open under arcing fault conditions due to lack of maintenance, twice the incident energy will be released.