The Elephant In The Room

By Jim Phillips | Sep 15, 2015
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“Properly” and “Maintained”—these two words always come up when discussing arc flash hazards. Why? Because protective devices such as circuit breakers and relays that have not been properly maintained may not operate as quickly as they should. During an arc flash, a longer duration will result in a greater total incident energy, creating an even greater hazard. 

Calculating the prospective incident energy from an arc flash depends on the available short-circuit current and the time it takes an upstream protective device to clear the fault. Graphs of the protective device’s tripping characteristic, known as time-current curves (TCC), are used to predict the time it takes a device to interrupt the arcing short-
circuit current. 

This may seem like a simple concept, but the question is whether the protective device actually operates as expected. The TCC indicates how fast a device should operate. Operation can depend on other factors, such as whether it was installed and maintained properly. 

Properly maintained—NFPA 70E

Language about properly maintained electrical equipment can be found in the 2015 NFPA 70E regarding “Normal Operation.” Five criteria must be met for certain tasks to be considered normal operation. Note No. 2 on the list: “130.2(A)(4) Normal Operation: Normal operation of electric equipment shall be permitted where all of the following conditions are satisfied. (1) The equipment is properly installed. (2) The equipment is properly maintained. (3) The equipment doors are closed and secured. (4) All equipment covers are in place and secured. (5) There is no evidence of impending failure.”

An informational note also states that the phrase “properly maintained” means the equipment has been preserved in accordance with the manufacturer’s recommendations and applicable industry codes and standards.

Chapter 2 further discusses maintenance requirements for electrical equipment. 

“205.3 General Maintenance Requirements: Electrical equipment shall be maintained in accordance with manufacturers’ instructions or industry consensus standards to reduce the risk associated with failure. The equipment owner or owner’s designated representative shall be responsible for maintenance of the electrical equipment and documenation.”

Applicable codes and standards

NFPA 70B, Recommended Practice for Electrical Equipment Maintenance, provides details about preventive maintenance for electrical, electronic and communication systems and equipment to prevent equipment failures and worker injuries. In addition, the Inter­National Electrical Testing Association (NETA) publishes standards for acceptance and maintenance testing of electrical power equipment.

Caveats and disclaimers

Some companies have qualified electrical maintenance personnel on staff and may be able to properly maintain electrical equipment. However, many companies don’t have that staffing luxury. 

During economic downturns, electrical maintenance can often be a target of budget cuts. Companies may defer maintenance in an attempt to reduce costs. From a financial perspective, this may seem like a good idea. However, from a safety perspective, if an accident occurs due to lack of maintenance, it can become a nightmare. 

When performing incident-energy calculations as part of an arc flash risk assessment, the maintenance and condition of protective devices can introduce some uncertainty. Will the devices operate according to their TCCs? To account for this uncertainty, a caveat or disclaimer will almost always be included. The language may be something like: “The results of this arc flash risk assessment are based on the equipment owner or the owner’s designated representative having maintained the electrical equipment in accordance with manufacturers’ instructions or industry consensus standards and that the protective devices operate in accordance with their respective time-current curves.”

Note that the above language is only an example. Consult legal council to develop such a disclaimer.

Don’t ignore it

Proper maintenance and testing of electrical power equipment is important for many reasons. However, when it comes to arc flash and electrical safety, proper maintenance of protective devices can make the difference between minimal or no injuries and the horrific alternative.

If your customer’s electrical system’s maintenance and testing has been ignored or is not up to date, it’s time to catch up. This is something that you cannot afford to ignore.

About The Author

PHILLIPS, P.E., is founder of and provides training globally.  He is Vice-Chair of IEEE 1584 Arc Flash Working Group, International Chair of IEC TC78 Live Working Standards and Technical Committee Member of NFPA 70E.  He can be reached at [email protected].






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