The standardization of the wiring process for the secondary circuits of the distribution cabinet and the effectiveness of anti-misoperation measures directly affect the stability of equipment operation and personnel safety. Regarding wiring techniques, the principle of "horizontal and vertical alignment, clear layering" must be strictly followed. Wire harnesses should be secured with nylon cable ties or binding wires, and the bundling spacing should not be too large. The fixing spacing of horizontal and vertical wire harnesses must be controlled within a reasonable range to ensure the wire harnesses are stable and aesthetically pleasing. There should be no joints in the middle of any wires; connectors must be located on the device terminals or terminal blocks to avoid poor contact due to loose connections. The stripped length of the wires should be appropriate, and when inserting them into the terminals, ensure that the copper core is not exposed and that the crimping is firm to prevent overheating or arcing caused by loose connections.
The cross-sectional area of the secondary circuit wires must be selected according to their function. Current circuits, which carry larger currents, require larger cross-sectional area wires to reduce resistance; low-voltage circuits, due to weak signals, require smaller cross-sectional area wires to reduce interference; and protective grounding wires must meet the thermal stability requirements when short-circuit current passes through them. All conductors should be kept away from arcing components to prevent arcing damage to the conductor insulation when circuit breakers, contactors, or other equipment operate. The connection between the ammeter and the shunt should be direct to avoid increasing contact resistance through terminals; the current loop should preferably be connected to the measuring instrument via test terminals for easy current measurement without disconnection.
Anti-misoperation measures require a comprehensive approach from design, construction, and maintenance. During the design phase, dual protection using mechanical and electrical interlocks should be employed. Mechanical interlocks achieve locking through component transmission; for example, when the switch trolley is in a non-operating position, the interlocking coil is not energized, preventing the closing shaft from rotating. Electrical interlocks use a series microswitch with normally open contacts to cut off the power supply to the closing circuit. During construction, strict adherence to the drawings is required, verifying the connection position of each conductor to avoid incorrect wiring due to misreading terminal numbers or wiring routes. For the voltage secondary circuits on both sides of the synchronization point, ensure that the three-phase voltage lines and neutral line from the same voltage transformer are placed on the same cable to prevent asynchronous grid connection accidents caused by voltage phase differences.
During maintenance, the insulation performance of secondary circuits must be checked regularly, paying particular attention to insulation degradation caused by moisture, aging, or mechanical damage. For relay protection circuits, relay contacts must be calibrated regularly to prevent poor contact due to oxidation of moving and stationary contacts. For example, in the main transformer cooler control circuit, if relay contacts are oxidized, it may trigger a complete cooler shutdown protection action, causing unplanned equipment outages. Furthermore, secondary circuit labeling management must be strengthened. Cable identification tags should include model, specifications, purpose, and routing information to facilitate quick fault location during maintenance.
Shielded cable connections must use a single-end grounding method. After the shielding wire is tightened, it should be crimped to the conductor through a lug. The crimped portion should be folded back over the outer layer of the insulated conductor to avoid electromagnetic interference affecting signal transmission. For single-strand conductors with small cross-sectional areas in low-voltage circuits, soldering or dedicated terminal blocks should be used for connection to prevent overheating due to insufficient contact area. Secondary wires must not pass between phases of the busbar to avoid wear on the conductor insulation layer due to busbar vibration.
The wiring process and anti-misoperation measures for the distribution cabinet secondary circuits must be implemented throughout the entire equipment lifecycle. From error-proofing logic design in the design phase to process control in the construction phase, and regular verification in the maintenance phase, every step must aim for "zero defects." Through strict process standards and multi-layered protection measures, the failure rate of secondary circuits can be effectively reduced, ensuring the reliable operation of the distribution cabinet under complex working conditions.
