Maintenance Triggered by Visual Inspection
Abnormalities in insulating components: Visible yellow discharge spots, black flashover marks, glaze loss, cracks, or damage to cemented joints on insulator surfaces necessitate a scheduled outage for maintenance to prevent future flashovers or insulator breakage.
Corrosion and deformation of metal parts: Extensive corrosion on transmission linkages, pins, or bases, or significant bending/deformation of crank arms and linkages, indicates a severe drop in mechanical strength; corroded or failed parts must be repaired or replaced immediately.
Abnormalities in contacts and connections: Visible ablation or blackening (oxidation) on moving and fixed contacts, loose terminal pad bolts, or discoloration due to overheating at lead connections indicate an immediate need for maintenance.
Maintenance Triggered by Quantitative Instrument Testing
Excessive overheating in the conductive circuit: Infrared thermography reveals temperatures exceeding 70°C at contacts or terminal pads, a temperature difference exceeding 20K between different points on the same phase, or significant temperature deviations across the three phases; an outage is required to polish contacts and tighten bolts to eliminate overheating risks.
Excessive circuit resistance: Circuit resistance values measured by a tester far exceed factory standards, with a deviation of over 30% between phases, indicating poor contact; immediate disassembly and maintenance are required.
Substandard insulation resistance: Testing with an insulation tester (megohmmeter) at the appropriate voltage level shows resistance below the minimum regulatory threshold, indicating insulation failure; an outage is required to investigate and repair insulation defects.
Failure of withstand voltage test: Flashover or dielectric breakdown occurs during the power-frequency AC withstand voltage test, indicating latent insulation defects; immediate maintenance or replacement of the faulty insulating component is required.
Maintenance Triggered by Operational Performance Verification
Abnormal opening/closing operations: Significant sticking, excessive resistance, or failure to open or close during manual or electric operation indicates corrosion or jamming in the transmission mechanism; the transmission components require disassembly, maintenance, and re-lubrication. **Non-compliant opening/closing positions: If, during slow-closing operations, the moving and fixed contacts of the three phases are found to make contact asynchronously (with the deviation exceeding permissible limits), or if contact insertion depth is insufficient or the contact opening distance fails to meet standards, the linkage travel must be readjusted and maintenance scheduled.
Failure of anti-misoperation interlocks: If the mechanical or electrical interlocks between the main disconnect switch and the grounding switch fail-rendering them unable to reliably prevent erroneous operations-immediate maintenance is required to restore interlock functionality and prevent serious accidents caused by operational errors.