A cable lug is the part that connects a conductor to a terminal, and it is where many heat-related failures begin. A lug that is too loose, crimped with the wrong die or made of the wrong metal gives a high-resistance joint, and a high-resistance joint turns current into heat. The factors below decide the right lug for a given cable.
| Selection factor | What to check |
|---|---|
| Conductor material | Use copper lugs on copper conductors and aluminium lugs on aluminium conductors. Where an aluminium conductor connects to a copper busbar or terminal, use a bimetallic lug or another method that prevents direct contact between the two metals. |
| Conductor size | The barrel must be rated for the conductor cross-section in sq mm. A lug marked for a different size will not crimp correctly. |
| Conductor class | Compacted stranded conductors and flexible conductors have different strand arrangements. Check that the lug is designed for the conductor class used. The classes are explained in the conductor class chart. |
| Palm and hole size | The hole must match the stud or bolt diameter of the terminal, and the palm must sit flat on the contact face. |
| Barrel type | Tubular lugs suit most power cable work. Long-barrel lugs hold the conductor over a longer length for high-current or high-vibration locations. |
| Crimp method | Use the tool and die the lug maker specifies. Crimp from the palm end towards the open end, and do not re-crimp over an old crimp. |
| Insulation and sealing | Cover the barrel and conductor exit with heat-shrink or an insulating sleeve suited to the voltage. |
Preparing an aluminium conductor
Aluminium forms an oxide film within moments of being cut. Clean the strands just before crimping, apply the jointing compound recommended by the lug maker, and crimp straight away. Skipping the cleaning step is a frequent cause of overheated aluminium terminations.
Checks after crimping
Inspect each crimp visually for a uniform indent and no strands outside the barrel. Pull the lug gently to confirm that it grips the conductor. Tighten the bolted joint to the torque stated by the terminal maker, and, after the cable has carried load, inspect the joint for discolouration, which indicates heat. Wider installation faults are covered in Most cable failures start at installation, not in the factory.
The cables these lugs terminate are described on the LV XLPE power cables page, which lists copper and aluminium conductors.