Why Do Loose Cable Terminals Become A "hidden Killer" Of Equipment Under Vibration?
In industrial settings, the reliability of wire lugs is directly related to the stable operation of the entire system. A frequency converter experienced a control signal interruption during commissioning due to loose terminal crimping. This is not an isolated case. When equipment is subjected to prolonged vibration, or if a torque wrench was not used during installation, the problem of exposed live wires after loosening of the electrical lugs connection becomes apparent, posing a "hidden killer" to personal safety and equipment operation.
The Chain Reaction of Hidden Faults
The exposure of live wires after loosening of the terminal lugs connection has a cascading effect. Loosening directly increases contact resistance, causing abnormal temperature rise when current flows. Heat accelerates metal surface oxidation, creating a vicious cycle that may eventually break down air insulation, leading to ground discharge or phase-to-phase short circuits. In a 6kV line accident, it was the cable head connection bolts that loosened due to overheating, ultimately causing the line to operate with a single phase.
From Torque Control to Connection Processes
To eliminate such hidden dangers, it is necessary to return to basic process standards. When connecting conductors to terminals, multi-core copper wires with a cross-sectional area greater than 2.5mm² must be connected to terminals. When tightening bolts, use torque tools and strictly follow the specifications to prevent slippage or loose connections. For multi-strand flexible wires, use appropriate tubular terminals and crimp them on four or six sides to effectively prevent the wire cores from loosening and slipping. If insulation restoration is required after maintenance, use insulating tape to wrap multiple layers in a semi-overlapping manner; do not simply rely on simple insulating tape, as this can cause it to age and loosen.
Special Risks in AC/DC Mixed Systems
In complex systems containing AC/DC circuits, the risk of exposed live wires after copper lugs loosening increases dramatically. When inspecting control boxes, if the core wire joints are not securely wrapped, exposed metal cores can easily allow AC current to enter the DC system. This incorrect AC/DC connection can cause relays in the control box to mis-energize, leading to erroneous circuit breaker tripping, amplifying a small mistake into a major accident causing equipment failure. Therefore, when working in confined spaces, exposed terminals must be effectively isolated and secured.
