To conduct maintenance and inspection of MCCB, perform the following:
• Clean all external contamination to permit internal heat dissipation.
• Inspect all surfaces for cracks or damage.
• Check for loose connections, and tighten circuit breaker terminals and bus bar connections. Use the manufacturer’s recommended torque values.
• Manually switch on and off the breaker in order to exercise the mechanism.
• Check for high-humidity conditions since high humidity will dete- riorate the insulation system.
• Check for hot spots typically caused by overheating due to termi- nation or connections being loose, high contact resistance, or inade- quate ventilation.
The following steps are recommended for servicing the switchgear enclosure, in addition to the maintenance recommendations made under medium- voltage switchgear:
• Turn power off and ground the bus. All dust and dirt should be vacuumed from the switchgear enclosure and components. Wipe clean buses, insulators, cables, and the like.
• Inspect bus work and disconnect for overheating. Tighten all mounting and splice bolts. Examine all connections for tightness.
• Check for alignment and seating of contacts of disconnecting devices.
Look for abnormal wear or damage.
• Clean and lubricate draw-out mechanism. Check operation of shutters, interlocks, and auxiliary devices.
• Clean ventilating openings and filters.
• After servicing, perform an insulation resistance test from phase to ground on each bus. Compare the results with previous tests to see any weakening tendency.
• Refinish damaged paint surfaces.