1. Preparation and preliminary inspection
Before conducting a comprehensive overhaul of the Power Distribution Cabinet after long-term operation, make full preparations. First, collect relevant information of the Power Distribution Cabinet, such as electrical schematics, installation manuals, operation records, etc., which will help maintenance personnel fully understand the structure and operation characteristics of the Power Distribution Cabinet. Then, cut off the power supply of the Power Distribution Cabinet and hang a signboard with the words "Do not close the switch, someone is working" in a conspicuous position to prevent danger caused by misoperation. At the same time, prepare the tools and equipment required for maintenance, such as insulation resistance testers, multimeters, torque wrenches, cleaning tools, etc.
Preliminary inspection of the appearance of the Power Distribution Cabinet to check whether the cabinet has signs of deformation, corrosion or damage. Check whether the cabinet door opens and closes smoothly and whether the door lock can work properly. For outdoor Power Distribution Cabinet, special attention should be paid to whether the protective facilities such as rain and sun protection are intact. In addition, observe whether the wiring in the Power Distribution Cabinet is neat and the markings are clear, which will help the efficient implementation of subsequent maintenance work.
2. Inspection of electrical components and connection parts
Inspect the electrical components in the Power Distribution Cabinet one by one. The circuit breaker is a key component. Check the wear of its contacts. If there are traces of ablation or severe wear on the contact surface, it may affect its opening and closing performance and needs to be repaired or replaced. At the same time, test the tripping characteristics of the circuit breaker to ensure that it can operate normally under overload, short circuit and other conditions. The contactor and relay should also check the contact condition, the insulation performance of the coil, etc., to see whether their operation is flexible and reliable.
Inspect the busbar and various connection parts. The surface of the busbar should not have obvious oxidation or discoloration. If there is slight oxidation, it can be cleaned and polished. Focus on checking whether the busbar connection bolts are loose, and use a torque wrench to tighten them according to the specified torque value, because loose connections will increase contact resistance, cause heating and even failures. At the same time, check the connection points of wires and cables to ensure that the connection is firm and the insulation layer is not damaged.
3. Inspection of secondary circuits and grounding systems
The secondary circuit plays an important role in the control and protection functions of the Power Distribution Cabinet. Check whether the wiring of the secondary circuit is firm, and use a multimeter to measure the on-off status of the line to ensure normal signal transmission. For the fuse in the secondary circuit, check whether the fuse is blown and whether the seat is in good contact. At the same time, check whether the setting values of various protection devices in the secondary circuit (such as overcurrent, overvoltage protection, etc.) are correct and whether the action is sensitive.
The maintenance of the grounding system is equally important. Check whether the connection between the grounding busbar and the cabinet is firm and whether the grounding bolts are loose. Measure the grounding resistance, and its value should meet the relevant standards (generally, the grounding resistance of the low-voltage system is not greater than 4Ω). If the grounding resistance is too large, it is necessary to find the cause and repair it, such as checking the buried depth of the grounding electrode, the humidity of the surrounding soil, etc., to ensure the effectiveness of the grounding system and protect the safety of people and equipment.
4. Testing and finishing work after maintenance
After the maintenance is completed, the Power Distribution Cabinet should be fully tested. First, conduct an insulation resistance test. Use an insulation resistance tester to measure the insulation resistance between each phase and between phases and the ground. The insulation resistance value should meet the specified standard (e.g., no less than 1MΩ for low-voltage Power Distribution Cabinet). Then conduct a power-on test. Close the switch under no-load conditions and check the working status of each electrical component, such as whether the indicator lights are lit normally and whether the instrument display is accurate. Gradually load the load and observe the operation of the Power Distribution Cabinet under different loads to ensure its stable operation.
