23-06-2012, 10:51 AM
PREVENTIVE MAINTENANCE OF ELECTRICAL EQUIPMENT AND PROTECTION DEVICES FOR BUILDINGS
PREVENTIVE MAINTENANCE OF ELECTRICAL EQUIPMENT.pdf (Size: 119 KB / Downloads: 92)
INTRODUCTION
More than two-thirds of electrical system failures can be prevented by a routine
preventive maintenance program. Studies show that 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 the preventive
maintenance schedule. In addition, a planned EPM program allows the equipment
owner to schedule the system outage at a time of their choose rather than having to
correct major problems resulting from an always untimely failure or breakdown.
Switchgears
Enclosures
Ensure that all enclosure panels, doors, and structures are well-maintained in
accordance with the manufacturer’s specifications. During off-line 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 build-up of dirt or
other contaminates that will not come off with vacuuming should be cleaned with
lint free rags using cleaning solvents recommended by the manufacturer.
Air & Vacuum Circuit Breakers
Insulation
Remove and clean interphase 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 sign of corona, tracking,
arcing or thermal or physical damage. Ensure that insulation is left clean and dry.
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.
INFRARED INSPECTION
An infrared, or thermographic, inspection should be performed at least once every
three years on all switchgear, distribution panels, cable and bus connections, motor
control centres and starters, and other critical equipment. Infrared inspections are
extremely beneficial in reducing electrical failures by identifying potentially
dangerous conditions; such as, loose or dirty connections, overloaded or imbalanced
circuits, or improperly installed equipment. By measuring the heat imbalance relative
to the environment and to surrounding equipment, abnormal or adverse conditions
can be uncovered that if left unattended would worsen to the point of failure.