Proper engineering on the front end of a project, including acceptance testing and commissioning prior to initially energizing, ensures a smooth start up and reduces the problems that can keep a facility from coming on line. Many studies also have shown that routine maintenance, including testing of electrical distribution equipment, has increased reliability and minimized downtime for commercial and industrial facilities.
The same can be said about protecting electrical workers who operate or work on energized electrical equipment, as we now can calculate that the incident energy produced by an arcing fault is proportional to its operating time. This aspect of incident energy means that proper maintenance and testing of over-current protective devices (OCPD) not only is an operational issue, but also a safety issue.
OSHA regulations and NFPA requirements for a qualified electrical worker emphasize the need for safety and skills training for electrical and non-electrical workers. An electrical worker may be experienced, but may not meet OSHA's definition of a qualified person if he or she lacks the safety training and skills required by 29CFR1910.332 and .333.
Tasks with the highest propensity for incidents are related to energized tasks such as troubleshooting (24 percent), operating electrical equipment (19 percent) and repairing components (18 percent). Maintaining electrical equipment only accounts for 5 percent of electrical incidents, as the equipment generally is de-energized to perform scheduled maintenance. Most of these incidents are due to workers not checking for the absence of voltage — or other oversights — before attempting to perform maintenance on the equipment.
NFPA 70E SAFETY-RELATED MAINTENANCE
The NFPA 70E Committee states that an electrical power system must be properly designed, properly installed and properly maintained in order to be considered safe to operate or to maintain. Article 200 (Introduction & Scope) in Chapter 2 of NFPA 70E offers general requirements for safety-related maintenance, but does not give any specific details about the methodology for performing electrical maintenance or the frequency to which the different vintages, manufacturers and protective devices should be maintained.
This largely is left up to the employer to develop and implement, based on manufacturer's instructions, literature and industry standards, as well as equipment condition and the facility's reliability requirements. These NFPA 70E requirements and procedures do, however, establish the requirement for a maintenance program that positively impacts safety for the electrical worker:
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Article 200.1 (1) — “These requirements identify only that maintenance is directly related to employee safety during activities such as installation, operation, maintenance and demolition activities.”
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Article 200.1 (2) — “Chapter 2 does not describe specific maintenance methods or test procedures. This is left up to the employer to choose from the various maintenance methods available to satisfy the requirements of Chapter 2.”
NFPA 70E references two national consensus documents: NFPA 70B — The Recommended Practice for Electrical Equipment Maintenance — and ANSI/NETA MTS-2007 — the Standard for Maintenance Testing Specifications — when discussing proper and safe maintenance of electrical equipment. In addition, two articles establish that a qualified worker is required to preserve and restore the equipment:
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Article 200.1 (3) — “For the purpose of Chapter 2, maintenance shall be defined as preserving or restoring the condition of the electrical equipment and installations for the safety of employees who work on, near or with such equipment. This maintenance directly impacts the proper functionality of the over-current protective devices and circuit breaker mechanical components, as well as any insulating systems and protective barriers.”
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Article 205.1 Qualified Persons — “Employees who perform maintenance on electrical equipment and installations shall be qualified persons as required in Chapter 1 and shall be trained in, and familiar with, the specific maintenance procedures and tests required.”
Article 205.3 states under general maintenance requirements that “Overcurrent protective devices (OCPD) shall be maintained in accordance with the manufacturers' instructions or industry consensus standards.” This requirement in NFPA 70E calls out for the need of specialized testing of over-current devices and mechanical timing to determine operator speeds, documentation of the testing and trending of the maintenance history of the equipment, all of which is crucial for establishing reliability and safety for an electrical worker.
PROTECTIVE DEVICES
With the increased distribution of molded case and insulated case products, the ability to inspect the internal mechanical components of the circuit breaker has become limited due to the time and expense required to perform this task. The manufacturer's warranty may be invalidated by breaking the case seal, and the OCPD also would lose its UL certification. Typically, most of these products are non-draw-out/bolted-in, further increasing times for removal and reinstallation, as well as the cost of testing. This creates a challenge for maintaining these products.
An NRC Report (NUREG/CR-5762, July, 1997) stated that 80 percent of the molded case products will not trip after 3-5 years of service. A more recent survey reported to the 2007 IEEE Electrical Safety Workshop by the Inter-National Electrical Testing Association (NETA) stated that roughly 22 percent of the 340,000 low- and medium-voltage protective devices that were surveyed had an issue that affected operation. This data closely correlated with the IEEE 493: Recommended Practice for the Design of Reliable Industrial and Commercial Power Systems.
The 2007 NETA Circuit Breaker Survey yielded accurate, specific data about the average condition of electrical equipment currently in service throughout the United States. Of the 22 percent of defective devices, an average of 10.5 percent did not function at all, 42.8 percent had mechanical issues, 51.4 percent had lubrication issues with the breaker mechanism or operator, 35.9 percent had issues related to the solid state programmer failure and 20.5 percent had issues with the magnetic latch or trip coil.
This data alerts an electrical worker to the fact that if he or she is involved in an electrical incident, there is a probability — depending on the equipment vintage and configuration — that he or she would have anywhere from a 22 percent to 80 percent chance of receiving traumatic burns or even death, even taking into consideration the arc flash analysis results, warning labels, their training and qualifications and the PPE he or she is wearing.
HAZARD ANALYSIS
Once a facility safety or maintenance manager makes the decision to perform arc flash hazard calculations, several key considerations must be made during the data gathering portion of the project. Article 130.3 of the 2009 NFPA 70E states that the arc flash hazard analysis shall take into consideration the design of the over-current protective device and its opening time, including its condition of maintenance. Two additional supporting statements in the reference notes state:
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“Improper or inadequate maintenance can result in increased opening time of the over-current protective device, thus increasing the incident energy.”
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“For additional direction for performing maintenance on over-current protective devices see Chapter 2, Safety-Related Maintenance Requirements.”
It is common for facilities and engineering firms to produce an arc flash hazard analysis using many of the available forms of software on the market. Most of the data inputted into the software comes from site evaluations, where specific information is gathered and entered into the software for calculating the incident energy as well as producing the warning labels and providing protective device settings. Typically, these software programs do not take into consideration the maintenance frequency, procedures or methodology.
This creates a huge challenge since most protective devices such as protective relays, circuit breakers and automatic switches often sit static in the closed position and do not operate for months or even years at a time. When these protective devices are called on to operate and interrupt faults, they may be slow, sluggish or may not even operate at all, due to the factory lubrication drying out over time. This creates a coordination nightmare and increases arc duration and incident energy exposure. This situation can render the best electrical safety programs, training and PPE useless and the arc flash hazard analysis invalid.
As the consensus grows that protecting electrical workers includes the maintenance of the electrical equipment and its protective components, it becomes very evident that there is no other way to meet OSHA's requirement for providing a safe workplace or NFPA 70E's requirement for maintaining OCPD without recent acceptance or maintenance testing data. Electrical workers also must receive training in electrical hazard awareness, which should include education to determine the reliability of the equipment he or she is operating or working on, as well as the upstream device that will be his or her first line of defense if an electrical incident occurs.
Mike Moore is sales manager for the Engineering Services Division of Shermco Industries Inc. in Dallas and the marketing director for OPMUG (Oklahoma Preventive Maintenance Users Group).
Best Practices for Electrical Maintenance Programs
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Write a safety- or reliability-based electrical acceptance testing plan for all new equipment to ensure that installation meets applicable codes, standards and safely operates as designed by the manufacturer.
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Develop an electrical maintenance plan for existing and service-aged electrical equipment that evaluates and trends insulation systems, mechanical operation and over-current protective devices for proper operation.
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Validate all over-current protective devices with the most recent coordination study settings.
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Develop these programs based on national consensus standards to bring credibility to the program. Sources such as the IEEE STD 902-1998 (Yellow Book) — Guide for Maintenance, Operation and Safety of Industrial and Commercial Power Systems, NFPA 70B — Recommended Practice for Electrical Equipment Maintenance — or the International Electrical Testing Association's ANSI / NETA MTS-2007 — Maintenance Testing Specifications — offer guidelines for the frequency of maintenance tests. ANSI/NETA MTS-2007 offers very specific recommendations in annex B.
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Implement programs such as “First Trip” to give the safety and maintenance manager an actual picture to the real world. A first trip program records the operating speed of a breaker when it is called on to operate on its first trip after being in service for some specified period of time.
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The consideration of equipment condition, environment, loading, criticality and reliability must be determined to correctly develop any maintenance program, and long-term trending, auditing and staying abreast of changes with standards and methods of test and evaluation must be considered as well.
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Perform an arc flash hazard analysis. During the data-gathering portion of arc flash analysis, all history and documentation relating to the maintenance frequency, procedures and methodology for all electrical equipment to be surveyed should be requested and submitted. The qualifications of the testing contractor should be evaluated as well. Details such as test equipment calibration, technician training, qualifications and experience are a must as part of evaluating the maintenance personnel who will perform the actual tests and maintenance. Utilization of nationally recognized testing standards always should be referenced in all maintenance reporting.