Installation Specifications and Routine Maintenance Points for Low-Voltage Complete Switchgear

Low-voltage complete switchgear is the end-core equipment of power distribution systems in industrial and mining enterprises. Its installation quality and maintenance level directly affect the power supply reliability of electrical equipment. This article provides complete operational guidance from installation, cabling to routine maintenance.

I. Installation Technical Requirements

Foundation and Environment

• The power distribution room floor should be level and dry, away from heat and water sources
• Sufficient operating and maintenance clearances should be reserved at the front and rear of the cabinets (front ≥1.5m, rear ≥0.8m)
• The power distribution room should be well ventilated, with ambient temperature not exceeding 40°C and relative humidity not exceeding 90%
• Levelness deviation of foundation channel steel should not exceed ±1mm/m, and total length not exceed ±3mm

Cabinet Installation

After positioning the cabinets, adjacent cabinets are connected and tightened with bolts. The verticality deviation of the entire row of cabinets should not exceed 1.5mm/m. Cabinets are spot-welded or bolted to the foundation channel steel. All cabinet earthing terminals should be securely connected to the main earthing busbar, forming a continuous earthing circuit.

II. Main Busbar Installation

The main busbars are usually copper bars. During installation, pay attention to:

• Lap surfaces should be smooth and clean, coated with an appropriate amount of conductive paste
• Bolt tightening torque must comply with specifications (for M12 bolts, typically 40N·m)
• Phase sequence arrangement is uniform (usually A-yellow, B-green, C-red, from top to bottom or left to right)
• Electrical clearance between phases and to earth should not be less than 20mm
• Spacing of busbar supporting insulators should meet design requirements

III. Cable Termination

• Cables should be arranged neatly with clear identification; incoming and outgoing cables should be fixed separately
• Cable terminal production should comply with process standards, and lug crimping should be firm
• Terminal bolt tightening torque should be appropriate – neither loose nor over-tightened
• The cable compartment of draw-out switchgear should have sufficient space for cable bending radius
• Secondary control cables should be laid separately from primary power cables

IV. Pre-commissioning Inspection

• Use a 500V megohmmeter to measure insulation resistance of the main circuit; it should not be less than 0.5MΩ
• Check tightness of all bolts, especially at busbar connections
• Manual opening and closing of circuit breakers should operate normally, and trip devices should act reliably
• Drawers should move in and out flexibly, and interlocking mechanisms should function properly
• Protection device settings should be verified and signal circuits complete
• The cabinet interior should be clean and free of debris; all doors should open and close freely

V. Routine Maintenance Points

Regular Inspections (recommended quarterly)

• Observe whether instrument indications are normal and whether there are any abnormal alarm signals
• Check busbar connections and circuit breaker contacts for signs of overheating or discoloration
• Use an infrared thermometer to measure temperatures at key connection points; temperature rise should not exceed 65K
• Listen for abnormal sounds inside the cabinet (such as discharge "buzzing" or arc sounds from poor contact)
• Check whether cabinet earthing conductors are intact
• Clean dust and foreign objects from inside the cabinet

Annual Maintenance

• De-energize and check tightness of all busbar connection bolts
• Contact resistance test of circuit breaker main contacts (not exceeding 120% of factory value)
• Insulation resistance test to ensure values remain within acceptable range
• Inspection and cleaning of primary and secondary plug-in connectors for draw-out cabinets
• Functional verification and setting recheck of protection devices

Common Abnormalities and Handling

• Contact overheating: De-energize and check contact surfaces, polish oxide layer, reapply conductive paste, and retighten
• Circuit breaker nuisance tripping: Check protection settings, load conditions, and eliminate external interference
• Drawer insertion/withdrawal difficulty: Check guides and plug-in connectors for deformation; clean and apply a small amount of lubricating grease
• Abnormal instrument readings: Check secondary wiring and transformer circuits for normality

Establishing comprehensive inspection records and annual maintenance archives is an effective means to achieve predictive maintenance and reduce the risk of unexpected power outages.