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Home / Download Center / Electrical Engineering Books and Technical Guides / Power substation guides / Preventive Maintenance And Reliability Of LV Overcurrent Protective Devices


The NEC – National Electrical Code states “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.”

Preventive Maintenance And Reliability Of LV Overcurrent Protective Devices
Preventive Maintenance And Reliability Of LV Overcurrent Protective Devices

With regard to circuit breakers, the only way to accomplish this is through proper maintenance and testing of these devices.

Several studies have revealed that if a circuit breaker has not been maintained, according the manufacturers’ instructions, for a period of five years, there is a 50% probability of failure of the circuit breaker.

The first step to properly maintaining electrical equipment and overcurrent protective devices is to understand and practice recommendations of electrical equipment maintenance from various sources. Examples of sources that could be used for this purpose include, but are not limited to, NFPA 70B, IEEE Standard 902 (Yellow Book), NEMA AB-4, NETA Specs, NFPA 70E-2000, and the Manufacturer’s instructions, as well as any applicable IEC standards.

The first step in the maintenance and testing of overcurrent protective devices is to provide adequate training and qualification for employees. NFPA 70E 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.”

Qualified Employees

The basic definition of a qualified person is one that is familiar with the construction and operation of the equipment and the hazards involved.

The Occupational Safety and Health Administration (OSHA) also requires an employee to demonstrate proficiency in the work practices involved before the employer can certify that they have been trained. It is vitally important that an employee be properly trained and qualified to maintain electrical equipment in order to increase the equipment and systems reliability, as well as the employee’s safety.

Title:Preventive maintenance and reliability of LV overcurrent protective devices – Michael Callanan, Dennis K. Neitzel (M. IEEE) and Dan Neeser (M. IEEE)
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Preventive maintenance and reliability of LV overcurrent protective devices

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