Initial Safety Isolation and Fault Diagnosis
First, rack the faulty draw-out unit to the "test" position. After opening the circuit breaker, use a transfer trolley to remove the unit entirely from the cabinet, ensuring complete physical isolation from the high-voltage busbar.
Conduct a systematic check based on the fault symptoms: if the unit closes manually but fails to close electrically, classify it as an electrical fault; if neither manual nor electrical operation works, prioritize checking for mechanical binding or jamming.
Use tools such as a multimeter and infrared thermometer to pinpoint whether the fault lies in the control circuit, contact system, or mechanical transmission mechanism, thereby avoiding indiscriminate disassembly that could exacerbate the problem.
Repair of Core Mechanical Faults
Draw-out unit chassis binding: Disassemble the guide rails to clean out accumulated dust and debris; apply molybdenum disulfide grease to gears and pivot pins; and realign any deformed positioning plates to ensure the unit moves in and out smoothly without binding.
Opening/closing mechanism binding: Open the mechanism panel to inspect springs, connecting rods, and dead-center positions; adjust the opening solenoid plunger stroke; and ensure the closing push-rod travels at least 2mm beyond the support bracket and that transmission components return fully to their reset positions.
"Five-Protection" interlock failure: Correct any misalignment in the mechanical interlock plates and smooth out any binding locking latches; verify that the draw-out unit cannot be moved after the circuit breaker closes and that the cabinet door cannot be opened when the grounding switch is engaged, ensuring full compliance with "Five-Protection" safety standards.