Achieving the Highest Quality Connections

Connecting Al and Cu wires to cable lugs through pre-rounding

Pre-rounding is a process where, for instance, a Cu or Al conductor is rounded before being installed into a cable lug. This procedure ensures that the conductors are compressed into the desired shape and density without damage. Pre-rounding maximises the contact between the wire and the cable lug, ensures proper tool operation, and both simplifies and accelerates installation.

Pre-rounding is especially important when working with screw-type cable lugs. Without pre-rounding, torque screws may break prematurely. This process also ensures that the tightening torque does not exceed the manufacturer’s installation instructions. Pre-rounding is, however, often overlooked or performed using incorrect tools, which leads to unprofessional and unreliable results. In the worst-case scenario, improper tools can damage the wire strands.

Pre-rounding and sleeving for sector-shaped Cu conductors

For sector-shaped copper conductors, the use of a pre-rounding sleeve is always recommended. The sleeve ensures the strands remain tightly bundled and rounded, thus improving the contact between the conductor and the cable lug. Additionally, the sleeve increases the conductor’s cross-sectional area at the connection point, compensating for the void caused by the compression of the copper wire. Specific sleeves are available for different cable types, such as the VHR353 sleeve for three-sector cables and the VHR354 sleeve for four-sector cables. Using the correct sleeves ensures connection quality and durability.

Pre-Rounding, brushing, and greasing for sector-shaped Al conductors

Preparing aluminium conductors involves pre-rounding, brushing, and greasing. After pre-rounding, the aluminium conductor must be brushed with a steel brush to remove the oxidised layer. This layer, formed when the metal reacts with oxygen in the air, can reduce electrical conductivity and compromise connection quality.

Important to note

Klauke Al and Al/Cu cable lugs and conductors come pre-filled with oxidation-breaking contact grease that eliminates the need to additionally brush and grease the conductors.

When installed in dry environments, copper pre-rounding sleeves can also be used with aluminium conductors. However, it should be noted that over time, the surface of aluminium-copper connections may oxidise, reducing connection quality. Therefore, copper sleeves are recommended for use exclusively with copper conductors.

What issues are commonly observed in connections?

The most frequently observed problems in inspections include loose or "fused" connections. In such cases, the temperature of the connection has risen excessively, causing the insulation to overheat and, in the worst cases, burn. Overheating issues are also prevalent in DC and solar power systems.

What problems arise in connections without pre-rounding?

Without proper pre-rounding, connections may become loose and overheat, potentially causing the connection to catch fire. In torque lugs, screws may remain at uneven heights, reducing connection durability. A loose connection can also result in the cable retracting or even detaching from the lug.

Why is pre-rounding important?

Pre-rounding ensures connection durability and safety by adhering to the cable and cable lug manufacturers’ guidelines, which often require sector-shaped conductors to be rounded before making the connection. Following these guidelines prevents overheating and minimises safety risks.

Why is pre-rounding often overlooked, or connections made carelessly?

Overlooking pre-rounding or performing poor-quality connections can result from ignoring or failing to read the manufacturer’s instructions.

What measures are taken to address observed issues?

Issues identified during inspections are addressed promptly. All deficiencies are recorded in the inspection report, and it is the installer’s responsibility to review and correct any errors. Additionally, installers and clients are informed about how to make connections in accordance with instructions and standards. It is worth noting that if connections were originally made following the manufacturer’s instructions, responsibility for their quality remains with the installer, even after the warranty period ends. Poorly made connections may not immediately show issues in thermal imaging but can manifest as loosening or overheating 2–3 years later.