Guide for an Electrical Preventive Maintenance (EPM) Program

Hello,and welcome back to Teckhme.Today we will present Guide for an Electrical Preventive Maintenance (EPM) Program.

Electrical equipment failures account for millions of dollars in damage and lost business every year. As this country’s electrical infrastructure continues to age, this problem is only going to worsen unless active steps are taken to counter the trend.Ironically, more than two-thirds of electrical system failures can be prevented by a routine preventive maintenance program. The failure rate of electrical equipment is three times higher for components that are not part of a scheduled preventive maintenance program as compared with those that are. In addition, a planned EPM program allows the equipment owner to schedule the system outage at a time of their choosing rather than having to correct major problems resulting from an always untimely failure.

The purpose of this guide is to provide the insured with typical practices and frequencies that would form the core of a regularly scheduled electrical preventive maintenance program. A preventive maintenance program should be developed, implemented, and completed by properly trained and qualified individuals. Actual maintenance activities and frequencies should be based on the specific operations and conditions of the equipment. Any electrical preventive maintenance program should be performed in accordance with accepted industry standards and safety practices.

Recommended maintenance practices

The following sections are segmented by equipment type. For each component, a recommended minimum practice for preventive maintenance is provided. Where applicable, additional suggested practices are presented for a more thorough EPM program.

  • Switchgear

1.Enclosures—Ensure that all enclosure panels, doors, and structures are well-maintained in accordance with the manufacturer’s specifications. During de-energized maintenance, enclosures are to be vacuum cleaned of all loose dirt and debris — use of compressed air is not recommended since this may cause foreign particles to become embedded in the insulation or damage insulators. Any buildup of dirt or other contaminants that will not come off with vacuuming should be cleaned with lint-free rags using cleaning solvents recommended by the manufacturer.

All vents and fan grills are to be cleaned of all dust and/or dirt accumulations. Ensure that ventilation openings are not obstructed. Where seals and/or gaskets are installed, these should be examined and repaired or replaced as necessary. All doors and access panels should be properly secured during operation. Where heater elements are installed, these should be cleaned, examined for damage and/or deterioration, and tested. Repair or replace heater elements as necessary.

Electrical equipment rooms or vaults should be kept cleaned of dirt and/or dust accumulations on a regular basis. Doors and windows should be maintained in proper working order and kept closed during routine operation. Access doors should be clearly marked to alert personnel that live electrical equipment is in use. Where ventilation and/or air conditioning is used,all fan motors should be cleaned and examined for signs of wear and deterioration. Fan  blades should be cleaned of dirt and  dust and bearings should be properly lubricated. Vent openings should be cleaned of all dust and dirt accumulations. Filters should be cleaned and/or changed as recommended by the manufacturer, or more often if conditions warrant. Electrical equipment rooms should never be used as storage areas.

Electrical equipment rooms or vaults should be examined for evidence of water seepage. The tops of electrical equipment enclosures should be examined for evidence of water since this is a common entryway that often goes undetected until a failure occurs. The source of the water should be immediately identified and corrective measures taken to permanently correct the condition.

2.Insulators, supports, and connectors—Inspect insulators and conductor supports for signs of cracking, broken pieces, and other physical damage or deterioration. Clean all loose dirt with lint-free rags. For contaminates that will not remove easily, solvents approved by the manufacturer may be used. Examine for evidence of moisture that may lead to tracking or flashover while in operation. Examine surrounding areas for signs of tracking, arcing, or overheating. Repair or replace damaged insulators and supports as necessary.

Examine all bolts and connecting devices for signs of deterioration, corrosion, or overheating. Ensure that bolts and connecting devices are tight, according to manufacturer’s specifications. Be careful not to over-torque bolts and connecting devices since insulators are easy to damage and difficult to replace. Where copper and aluminum conductors and/or connectors are used together, examine connections for signs of galvanic action. Ensure that the connectors are properly used and installed in accordance with manufacturer’s specifications. Apply an antioxidant compound to all aluminum to copper connections.

3 Conductors—Examine insulation for signs of deterioration, cracking, flaking, or overheating. Examine all connections for signs of overheating, cracked or broken connectors, and signs of tracking or arcing. Ensure that conductors are clean and dry. Examine and clean all connections, and torque to manufacturer’s recommendations.

  • Air circuit breakers

1.Insulation—Remove and clean inter-phase barriers. Clean all insulating materials with vacuum and/or clean, lint-free rags. If it is necessary to use cleaning solvents, use only solvents recommended by the manufacturer. Inspect for signs of corona, tracking, arcing, or thermal or physical damage. Ensure that insulation is left clean and dry.

2.Contacts—Ensure that all contacts are clean, smooth, and in proper alignment. Ensure that spring pressures are maintained according to manufacturer’s specifications. On silver contacts, discoloration is not usually harmful unless caused by insulating deposits. Clean silver contacts with alcohol or silver cleaner using non-abrasive cloths.

Manually close breaker to check for proper wipe, contact pressure, contact alignment, and to ensure that all contacts make at approximately the same time. If possible, a contact resistance test should be performed to determine the quality of the contacts.

Older breakers equipped with carbon contactors generally require very little maintenance. Examine for proper pressure, deterioration, or excessive dressing which may interfere with their proper operation.

Draw-out contacts on the circuit breaker, and the stationary contacts in the cubicle should be cleaned and inspected for overheating, alignment, and broken or weak springs. Coat contact surfaces with contact lubricant to ease mating 

3 Arc interrupters—Clean all ceramic materials of loose dirt and examine for signs of moisture, and make sure the assemblies are clean and dry. Examine for cracked or broken pieces. Dirt and arcing deposits may be removed by light sanding — do not use emery cloth or wire brushes which may leave conductive residue behind. Repair or replace as necessary.

Examine arc chutes for dirt and/or dust accumulations and clean as necessary. Dielectric testing of arc shields may be recommended by the manufacturer. Check air puffer for proper operation.

4.Operating mechanism—Inspect for loose, broken, worn, or missing parts (consult manufacturer’s schematics for required parts). Examine for excessive wear of moving parts. Observe that operating mechanisms function properly without binding, hanging, or without delayed action. Ensure any lubrication is done according to the manufacturer’s specifications.Ensure mechanisms are clean, properly lubricated, and all bolts and screws are properly secured. Repair or replace as necessary.

5.Auxiliary devices—Inspect operating devices for proper operation and general condition. Ensure all indicating devices are fully functional and properly set. Protective relays and circuit breaker trip devices should be inspected and tested according to manufacturers’ specifications and applicable industry standards such as those issued by the Institute of Electrical and Electronics Engineers (IEEE) and the National Fire Protection Association (NFPA).

  • Vacuum circuit breakers
All maintenance is similar to that performed on air circuit breakers. As always, it is recommended that the manufacturer be consulted for specific maintenance and testing procedures. The integrity of the vacuum chamber is often tested by applying a test voltage across the open contacts of the breaker. However, this can be a destructive test and is therefore not recommended by HSB.

  • Air disconnect switches

Inspect and clean insulators and conductors as with circuit breakers. Tighten connections in accordance with manufacturer’s specifications. Do not over-tighten as this may result in damage to connectors.

If cleaning solvents are used, ensure that they are used as recommended by the manufacturer. Where abnormal environmental conditions exist, more frequent inspection and cleaning may be required.

Check the operation of the arc blades, if applicable, and ensure proper wipe of the main contacts. Inter-phase linkages and operating rods should be inspected to make sure that the linkage has not been bent or distorted and that all fastenings are secure. The position of the toggle latch to the switch operating linkage should be observed on all closed switches to verify the switch is mechanically locked in a closed position. Operate switch manually several times to ensure proper operation, and then by motor if power-operated. Ensure that all moving parts are properly secured and lubricated as specified by the manufacturer.

Contact resistance testing of each phase contact should be performed. The results should be recorded and analyzed to ensure proper contact is being made. If the contact resistance of the switch exceeds recommended minimums, repair or replace the switch immediately

  • Oil circuit breakers

1.External—Inspect the enclosure for signs of oil leakage. Clean external bushings assemblies and examine for signs of deterioration, tracking, and loose or broken parts. Observe oil gauge to ensure device is operating properly and measuring the oil level accurately.
2.Insulating oil test—Conduct a dielectric screen test of the insulating fluid. Based on the results of this test, filter or replace oil as required. Heavy carbon content can indicate potential contact wear and should be investigated further.
3.Internal—Since the contacts for oil circuit breakers are not readily accessible for inspection, the contact resistance should be tested as a minimum.
More extensive maintenance on the contacts might require draining the oil and dropping the tank, and is therefore performed less frequently. Follow manufacturer’s recommended schedule for examination of internal components such as contact inspections. Open breaker and examine contacts for wear and/or excessive deterioration. Examine linkages for loose, broken, or missing parts; repair or replace as necessary.
4.Auxiliary services—Operating mechanisms should be maintained as with air circuit breakers. Where applicable, examine oil level indicators, sight glasses, oil lines, gaskets, and tank lifters for proper conditions. Repair or replace as necessary and in accordance with manufacturer’s recommendations.

  • Molded-case circuit breakers

Molded-case circuit breakers should be kept clean for proper ventilation of the breakers. These types of breakers are usually tripped by a thermal element that senses an increase in temperature due to excessive current draw. However, if dirt accumulates on the surrounding edge of the breaker, the heat build-up may not be permitted to dissipate properly and result in nuisance tripping.

Clean the breaker housing and inspect it for cracks or signs of overheating. Tighten all connections. Exercise the breaker several times to ensure the mechanism has freedom of movement and to allow contact wiping.

In addition, larger duty circuit breakers (225 amps or above) should be electrically trip tested to ensure proper operation of the trip elements and trip linkages. Refer to the latest edition of the National Electrical Manufacturers Association (NEMA)Standard AB4, Procedures for Verifying Field Inspections and Performance Verification of Molded-Case Circuit Breakers. If possible, test contact resistance to ensure quality of breaker contacts.

All molded-case circuit breaker panels should be cleaned of all dirt, dust, and debris using a vacuum.

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