Daily Inspection Of Distribution Boxes

Routine inspection of distribution boxes is a crucial step in ensuring electrical safety and preventing electrical fires and equipment malfunctions. It is a systematic and highly specialized task, requiring inspectors to strictly adhere to safety operating procedures, maintain thorough inspection records, and promptly identify and eliminate potential hazards to ensure the safe and reliable operation of the power supply and distribution system.

1. Visual Inspection
Box Body: Inspect the distribution box casing for deformation, damage, rust, etc. Obvious dents, holes, or rust and peeling of metal parts may lower the protection level, making it easier for dust and moisture to enter and cause short circuits. Pay special attention to the corners and hinges, as these areas experience concentrated stress and are at higher risk of damage.

Box Door Sealing: The box door should close easily and seal well, with no signs of aging or detachment of the sealing strip. The grounding braided wire connecting the box door and the box body must be intact-the metal door of the distribution box/cabinet should be connected to the frame using a yellow-green insulated copper core flexible wire with a cross-sectional area of ​​not less than 4mm². Poor grounding may cause electrostatic discharge or electric shock hazards. The cabinet door should be locked, and the key should be kept by a designated person to prevent unauthorized opening and potential electric shock or misoperation accidents.

Surface Temperature and Odor: Gently touch the surface of the cabinet with the back of your hand. During normal operation, there should be no noticeable heat. If some areas are excessively hot or even scalding to the touch, it may indicate internal component overload or poor contact. Also, check for any burnt or plastic odors, as these are often warning signs of overheating wiring or aging insulation.

Warning Signs: The distribution box (cabinet) door should bear a clear and securely attached "Caution: Electric Shock" safety warning sign. The distribution device casing should be reliably grounded, and the grounding or neutral connection should be secure without any looseness, broken wires, or other abnormalities.

2. Internal Component Inspection

Circuit Breaker/Air Switch: Check that the switch markings are clear and match the actual control circuit; the operating handle should be flexible and free from jamming or looseness. If the switch casing is discolored, shows signs of burning, or trips repeatedly, it may indicate overload, short circuit, or component aging, and should be stopped and inspected immediately.

Residual Current Device (RCD): Test the RCD's test button. It should trip quickly and reset normally after being pressed. The rated residual current and tripping time on the RCD's nameplate must meet safety standards. If there is no response or the tripping is insensitive, it must be replaced promptly.

Terminal Wiring: All terminals should be securely fastened. Wires at the terminals should not have damaged or exposed insulation. Multi-strand wires must be fitted with lugs; direct winding of wires is prohibited. No more than two wires should be connected to the same terminal. Internal wiring should be neatly arranged, with clear color differentiation for phase (L), neutral (N), and ground (PE) wires (red/yellow/green for phase, light blue for neutral, and yellow-green for ground). Mixing or incorrect wiring is strictly prohibited.

Fuses: The fuse model and specifications must match the circuit load. Substituting fuses with non-standard components or objects such as iron wire, copper wire, or nails is strictly prohibited.

Instruments and Indicator Lights: Check that all displays and indicator lights on the cabinet/box are functioning correctly. Instrument displays should be clear and accurate, and switches and control buttons should be flexible and reliable.