I. Purpose: To ensure the normal and safe operation of low-voltage switchgear and various equipment control cabinets.
II. Scope: Applicable to low-voltage switchgear rooms, switchgear, and control cabinets of various equipment. Refer to relevant clauses for specific situations.
III. Responsibilities: The maintenance group of the Electromechanical Installation and Maintenance Engineering Department shall conduct a comprehensive inspection and maintenance every six months, completing the maintenance work within the shortest possible power outage time.
IV. Content
1. Preparation work:
A. Notify residents of the power outage start and end times one day before the switchgear power outage maintenance.
B. Complete all preparations before the power outage, especially ensuring that all tools are ready; and complete the maintenance work within the shortest possible power outage time.
2. Maintenance procedure:
A. Implement segmented maintenance, starting with the security load section.
B. Cut off the security load power; other loads are normally supplied with mains power. Disconnect the air switch supplying mains power to the security load, disconnect the generator air switch, set the generator selector switch to the stop position, disconnect the positive and negative battery cables, and hang a sign to prevent the generator from generating electricity.
C. Check the busbar joints for deformation and discharge blackening marks, tighten the connecting bolts, replace rusty bolts, and ensure that the joints are tightly connected. Check the insulation on the busbar for looseness and damage.
D. Manually pull out the total air switch from the switchgear, check the main contacts for signs of melting, check the arc extinguishing hood for blackening and damage, tighten all wiring screws, clean the dust inside the cabinet, and test the mechanical switching on and off conditions.
E. Remove each sub-switchgear from the drawer cabinet, tighten all wiring terminals. Check the installation and wiring of the current transformers, ammeters, and watt-hour meters, check the flexibility and reliability of the handle operating mechanism, tighten the air switch input and output lines, and clean the dust inside the switchgear and behind the switchgear.
F. When maintaining the capacitor cabinet, first disconnect the capacitor main switch, discharge the capacitors one by one to ground using a wire with a cross-sectional area of 10MM2 or more, then check whether the contactor, capacitor wiring screws, and grounding device are in good condition, check the capacitors for bulging, and clean the dust inside the cabinet with a vacuum cleaner.
G. After the security load section maintenance is completed, the generator can be started to supply power to it, and the mains power can be stopped to maintain the busbar section.
H. Sequentially disconnect the low-voltage side air switches, then disconnect the high-voltage side vacuum circuit breaker supplying power to the transformer, close the grounding switch, and hang a sign indicating "Do not close, personnel working".
I. After completing the maintenance of the switchgear according to items C, D, E, and F, remove the safety devices, disconnect the high-voltage side grounding switch, close the vacuum circuit breaker, and after observing that the transformer is put into operation without error, sequentially energize the low-voltage switchgear, and switch the security load power supply from the generator to the mains power.
V. Safety Precautions
1. Conduct voltage testing after power outage.
2. When performing segmented maintenance on the switchgear, an isolation device should be installed at the junction between the energized and de-energized switchgear.
3. When operating the high-voltage side vacuum circuit breaker, wear insulated boots and gloves, and have a dedicated person supervise.
4. When maintaining the capacitor cabinet, do not touch the capacitors before discharging them to ground.
5. Before energizing after maintenance is completed, check whether any tools are left inside the switchgear.
VI. Relevant Documents and Records
1. Maintenance work permit;
2. Annual maintenance records of switchgear and control cabinets;
3. Equipment maintenance records.
