1. Maintenance should begin from the low-voltage side of the transformer. After de-energizing the distribution cabinet, clean the dust inside, check the busbar and downlead connections for good condition, and check for overheating or discoloration at the joints. Check the cable heads and terminal blocks for secure connections, and check the grounding wires for corrosion and tightness. Ensure all secondary circuit connections are reliable and insulation meets requirements.
2. When inspecting drawer-type switches, the drawer-type switch cabinet should move smoothly when pushed in or pulled out, and the mechanical interlocking should be reliable. Check that the automatic air switch operating mechanism on the drawer cabinet is in place and that the wiring screws are tight. Clean the contactor contact surface and surrounding area of dirt, and check the contactor contact for good contact. If contact is poor, the contact surface can be slightly filed if necessary. If the contact is severely burned (the contact point is worn down to 1/3 of its original thickness), the contact should be replaced. Power indicators and indicator lights should be in good working order.
3. When overhauling the capacitor bank, first disconnect the main switch. Use a wire of at least 10mm² to discharge each capacitor to ground one by one. Visually inspect the casing for damage and oil leakage. If the capacitor casing is swollen, address the issue promptly by replacing the discharge device, control circuit wiring screws, and grounding device. After closing the circuit breaker, test the indicating and automatic compensation sections.
4. When overhauling circuit breakers in the receiving cabinet and interconnecting cabinet, first disconnect all loads, then use the handle to crank out the circuit breaker. Retighten the wiring screws and check if the spring force of the blades meets specifications. Check for cracks or damage to the arc-extinguishing grid. Manually test the mechanical interlock for accurate opening and closing. Check for good contact of the contacts; if necessary, file the contact surface. Check internal springs, washers, and screws for looseness, deformation, or detachment.