Cross-Bonding vs. Straight Joints: Choosing the Right Cable Accessory for MV/HV Networks

Cable joints are unavoidable in any extensive underground network — cable comes in finite manufactured lengths, and every connection point needs a joint engineered to restore the cable's original insulation performance across the splice. Two of the most common joint configurations are straight joints and cross-bonding joints, and choosing between them depends heavily on the voltage class and length of the cable run involved. Here's how to think about that choice.

Straight Joints: The Baseline Connection

A straight joint does exactly what its name suggests — it connects two cable ends of the same conductor, restoring continuity of the conductor, insulation, and screen/shield across the connection point, without altering the cable's electrical configuration.

Straight joints are the standard choice for most MV distribution cable connections and for shorter HV cable runs, where the additional complexity of cross-bonding isn't necessary.

Why Cross-Bonding Exists

For longer HV and EHV cable circuits, a different problem emerges: circulating currents. In a standard cable configuration where all three phase cables' metallic screens are bonded and grounded at both ends, the magnetic field generated by current flowing in the conductors induces a voltage in the screens — and if those screens form a closed loop, this drives circulating currents that generate additional heat losses and reduce the cable's effective current-carrying capacity.

Cross-bonding addresses this by dividing the cable route into sections (called "minor sections") and transposing — cross-connecting — the screen connections between sections in a way that theoretically cancels out the induced voltages over a complete major section (typically three minor sections), significantly reducing circulating current losses.

When Cross-Bonding Is Worth the Complexity

Cross-bonding introduces additional joint complexity, additional link boxes, and additional points of potential failure compared to straight, solidly bonded joints — so it's not used indiscriminately. It becomes worthwhile primarily for:

• Longer HV/EHV cable circuits, where circulating current losses would otherwise meaningfully reduce cable ampacity or waste significant energy
• High-current applications, where the magnitude of circulating currents (and their associated losses) is large enough to justify the added complexity
• Projects where maximizing cable capacity matters, since cross-bonding can allow a smaller conductor size to carry the same effective current compared to a solidly bonded configuration

Design and Installation Considerations

Cross-bonding systems require careful engineering: minor section lengths should be reasonably balanced to achieve effective cancellation, link boxes need surge protection (sheath voltage limiters) to handle transient voltages during fault conditions, and joint installation quality is critical, since cross-bonding joints are inherently more complex than straight joints and installation errors can compromise the entire scheme's effectiveness.

Making the Right Choice

For most MV distribution work and shorter HV runs, straight joints remain the simpler, more cost-effective, and entirely appropriate choice. For longer HV and EHV circuits — particularly in transmission applications — cross-bonding is often essential to achieving the cable's rated capacity and avoiding unnecessary losses.

Taban Niroo manufactures both silicone joint solutions for cross-bonding and straight configurations, engineered to support reliable performance across MV and HV cable networks.

Working through a joint configuration decision for an HV cable route? Our team can help evaluate whether cross-bonding makes sense for your specific circuit length and loading.