How Important is Electrical Equipment Maintenance?

How Important is Electrical Equipment Maintenance?

12/23/2016

How Important is Electrical Equipment Maintenance?
 
Introduction

This article provides insight into the maintenance requirements for overcurrent protective devices and the potential impact on the arc flash incident energy when maintenance is not performed properly. Electrical preventive maintenance and testing is one of the most important functions to be performed in order to maintain the reliability and integrity of electrical distribution systems, as well as for the protection of equipment and personnel. However, preventive maintenance of electrical systems and equipment, specifically with regard to overcurrent protective devices is often overlooked, or is performed infrequently or inadequately. An unintentional time delay in the operation of a circuit breaker, due to a sticky operating mechanism, can cause the incident energy of an arc flash to rise, sometimes dramatically.
 
The National Electrical Code (NEC) states that overcurrent protection for conductors and equipment is provided to open the circuit if the current reaches a value that will cause an excessive or dangerous temperature in conductors or conductor insulation. With regard to circuit breakers the only way to accomplish this is through proper maintenance and testing of these devices, per the manufacturer’s instructions. [1]
 
MAINTENANCE AND TESTING CONSIDERATIONS

Specific maintenance and testing procedures will not be addressed in this article, however, there are three important steps that should be considered when addressing the maintenance and testing requirements for overcurrent protective devices.
 
  1. The first step in properly maintaining electrical equipment and overcurrent protective devices is to understand the requirements and recommendations for electrical equipment maintenance from various sources. Examples of sources include, but are not limited, to the Manufacturer’s Instructions, ANSI/NETA MTS [2], NFPA 70B [3], IEEE Std. 3007.2, [4]; NEMA AB-4 [5], and NFPA 70E [6].
 
  1. The second step is to provide adequate training and qualification for employees. NFPA 70E, Section 205.1 states: Employees who perform maintenance on electrical equipment and installations shall be qualified persons…and shall be trained in and familiar with, the specific maintenance procedures and tests required. [6]
 
The Occupational Safety and Health Administration (OSHA), defines a qualified person as “One who has received training in and has demonstrated skills and knowledge in the construction and operation of electric equipment and installations and the hazards involved.” It is important that employees are properly trained and qualified to maintain electrical equipment in order to increase the equipment and system reliability, as well as enhance employee safety for all who work on, near, or interact with the equipment. [7]
 
NFPA 70E states, with regard to electrical equipment maintenance [6]:
 
  • Section 90.2(A), This standard addresses electrical safety-related work practices, safety-related maintenance requirements, and other administrative control for employee workplaces … In an informational note to paragraph 110.1(A) it explains that “administrative controls” include verification of proper maintenance and installation, alerting techniques, auditing requirements, and training requirements provided in the standard.
  • Section 110.1(B), Maintenance, was added to the 2015 edition of NFPA 70E to require the condition of maintenance as a part of the overall electrical safety program
  • Section 130.5 Arc Flash Risk AssessmentTake into consideration the design of the overcurrent protective device and its opening time, including its condition of maintenance
  • Section 205.3, Electrical equipment shall be maintained in accordance with manufacturers’ instructions or industry consensus standards to reduce the risk of failure and the subsequent exposure of employees to electrical hazards.
  • Section 205.4, Overcurrent protective devices shall be maintained in accordance with the manufacturers’ instructions or industry consensus standards. Maintenance, tests, and inspections shall be documented.
  • Section 225.3, Circuit breakers that interrupt faults approaching their ratings shall be inspected and tested in accordance with the manufacturers’ instructions.
  1. The third step is to have a written, effective Electrical Preventive Maintenance (EPM) program. NFPA 70B makes several very clear statements about an effective EPM program as follows [3]:
  • Electrical equipment deterioration is normal, but equipment failure is not inevitable. As soon as new equipment is installed, a process of normal deterioration begins. Unchecked, the deterioration process can cause malfunction or an electrical failure. An effective EPM program identifies and recognizes these factors and provides measures for coping with them.
  • In addition to normal deterioration, there are other potential causes of equipment failure that can be detected and corrected through EPM. Among these are load changes or additions, circuit alterations, improperly set or improperly selected protective devices, and changing voltage conditions.
  • A well-administered EPM program will reduce accidents, save lives, and minimize costly breakdowns and unplanned shutdowns of production equipment.
  • NFPA 70E, Chapter 2, Safety-Related Maintenance Requirements – … these requirements identify only that maintenance directly associated with employee safety … it does not prescribe specific maintenance methods or testing procedures. It is left to the employer to choose from the various maintenance methods available to satisfy the requirements.
 
As noted in NFPA 70E, Chapter 2, the maintenance requirements are necessary for employee safety, but this chapter does not specify reliability issues, although properly maintaining equipment will have an impact on the reliability of the electrical equipment and systems. [6]
 
IEEE Std 3007.2 states: In planning an electrical preventive maintenance (EPM) program, consideration must be given to the costs of safety, the costs associated with direct losses due to equipment damage, and the indirect costs associated with downtime or lost or inefficient production. [4]
 
All maintenance and testing of electrical protective devices must be accomplished in accordance with the manufacturer’s instructions. In the absense of the manufacturer’s instructions, the latest edition of the ANSI/NETA MTS [2] is an excellent source of information for performing the required maintenance and testing of these devices. However, the manufacturer’s time-current curves would be valuable information for properly testing each overcurrent protective device.
 
ARC FLASH HAZARD CONSIDERATIONS

Maintenance and testing are essential to ensure proper protection of equipment and the safety of personnel. With regard to personnel protection, NFPA 70E requires an arc flash risk assessment be performed before anyone approaches exposed energized electrical conductors or circuit parts that have not been placed in an electrically safe work condition. NFPA 70E, Section 130.5 states that the arc flash risk assessment must take into consideration the design of the overcurrent protective device and it’s opening time, including its condition of maintenance. [6]
 
All calculations for determining the incident energy of an arc flash require the arc clearing time of the overcurrent protective device. This clearing time is derived from the settings on the divice, along with the time-current curves. This information can also be obtained from a current engineering protective device coordination study, which is based on what the protective devices are supposed to do. If, for example, a low-voltage power circuit breaker has not been operated or maintained for several years and the lubrication had become sticky or hardened, the circuit breaker could take several additional cycles, seconds, minutes, or longer to clear a fault condition. This unintentional time delay could have catistrophic consequenses, due to the increase in incident energy, should an arc flash occur.
 
If the worker is protected based on what the circuit breaker is supposed to do and an unintentional time delay occurs, the worker could be seriously injured or killed because he/she was under protected. Maintenance is extremely important to an electrical safety program. Maintenance must be performed according to the manufacturer’s instructions, or industry consensus standard, in order to minimize the risk of having an unintentional time delay in the operation of the circuit protective devices.
 
CONCLUSION
 
In order to protect electrical equipment and personnel, proper electrical equipment preventive maintenance must be performed. The manufacturer’s instructions, or industry consensus standards, exist to assist users with electrical equipment maintenance and testing. When the overcurrent protective devices are properly maintained and tested for proper adjustments and operation, equipment damage and arc flash hazards can be limited as expected. Unfortunately many in industry think that just because the lights are on or the machines are running that everything is okay and that maintenance is not needed, because the circuit breaker is working just fine. No, the circuit breaker is not working, it is closed. Working is when an overload, ground-fault, or short-circuit occurs and the circuit breaker opens automatically in the time specified or when it is manually opened or closed. Maintenance of overcurrent protective devices is critical to electrical equipment and systems reliability, as well as for safety of personnel.