Across Australia’s harsh climatic zones—cyclonic northern regions, arid mining belts and coastal industrial corridors—the integrity of the earthing network determines infrastructure survivability.

When lightning strikes or high-voltage faults occur, the greatest risk is not simply current magnitude, but voltage difference between conductive systems. This phenomenon, known as Earth Potential Rise (EPR), can create lethal touch voltages and destructive flashovers.

Equipotential Bridging Bars are engineered to eliminate these dangerous voltage gradients by bonding multiple earthing systems into a unified low-impedance node.

They are fundamental to compliance with AS/NZS 1768 and AS/NZS 3000.

Earth Potential Rise and Transient Impedance

During a lightning event, a down-conductor can inject tens or hundreds of kiloamps into the lightning earth electrode.

Because of conductor impedance, that electrode may instantly rise to thousands of volts relative to other earthing systems.

Without equipotential bonding:

• Side-flashing may occur • Equipment insulation may fail • Sensitive electronics may be destroyed • Personnel may be exposed to hazardous touch voltage

Equipotential Bridging Bars interconnect:

• Electrical protective earth (PE) • Lightning protection system (LPS) earth • Telecommunications signal reference ground • Structural steel bonding

The goal is simultaneous potential rise across all bonded systems, eliminating voltage differential.

For lightning events, inductance dominates over resistance.

Because lightning has a rapid rise time, the governing relationship is:

V = L × di/dt

This means bonding conductors must be:

• Short • Straight • Wide • Low inductance

Heavy copper bars and flat copper tapes are preferred to reduce surge impedance.

AS/NZS 1768 and Transient Earth Clamps

AS/NZS 1768 requires equipotential bonding between systems, particularly in structures with lightning protection.

In noise-sensitive facilities such as data centres, direct DC bonding between “clean” signal earth and “dirty” lightning earth may create ground loop interference.

In these cases, bridging bars often support:

• Transient Earth Clamps (TEC) • Spark gaps • Surge isolation devices

Under normal conditions, systems remain isolated.

When surge voltage exceeds a breakdown threshold, the clamp conducts and equalises potential instantaneously.

Once the surge dissipates, isolation is restored.

The bridging bar acts as the mounting and bonding manifold for these devices.

Material Composition and Corrosion Resistance

Equipotential Bridging Bars must be manufactured from high-conductivity copper.

Common grades include:

• C11000 electrolytic copper • Oxygen-Free High Conductivity (OFHC) copper

In coastal or industrial environments, corrosion resistance is essential.

Tin-plated copper bars are preferred because:

• Tin resists sulphur and salt exposure • Surface oxidation is minimised • Contact resistance remains low

Fixings must be stainless steel or compatible alloys to prevent galvanic corrosion.

All bolted joints must maintain low impedance for the life of the installation.

Busbar Geometry and Thermal Withstand

Lightning impulses may exceed 200kA peak current.

The cross-sectional area of the bridging bar must withstand:

• Thermal rise during impulse • Electrodynamic forces • Mechanical stress

Typical bar dimensions may include:

• 50mm × 6mm • 75mm × 10mm • 100mm × 10mm

Engineering calculations must confirm that current density remains within safe limits and that temperature rise does not exceed cable insulation thresholds.

Installation and Isolation Support

A bridging bar must remain electrically isolated from unintended conductive surfaces.

It cannot be mounted directly onto steel enclosures or structural members.

SCHNAP Electric Products supports compliant installation with:

• Red DMC standoff insulators • Heavy-duty copper lugs • Disconnect links • Conductive jointing compound • Spring washers for vibration resistance

Standoff insulators provide:

• High dielectric strength • Mechanical rigidity • Secure separation from mounting surfaces

Disconnect links allow individual earth electrodes to be isolated during periodic testing without dismantling the entire bonding network.

Periodic Testing and Maintenance

Bridging bars must support ongoing verification including:

• Earth resistance testing • Continuity testing • Surge protection inspection

Low-resistance joints are critical.

Gas-tight bolted connections, properly torqued and treated with conductive compound, ensure long-term reliability.

Procurement and Compliance Assurance

Undersized brass bars or decorative “earth strips” are unsuitable for lightning bonding applications.

Correct selection requires:

• Verified copper purity • Adequate cross-sectional area • Pre-drilled hole pattern compatibility • Compliance with AS/NZS standards

Specialised electrical wholesalers assist in selecting bridging bars suited to:

• Telecommunications facilities • Industrial plants • Healthcare facilities • Data centres • Mining operations

SCHNAP Electric Products complements these systems with compliant termination and mounting accessories to maintain low impedance and long-term durability.

Conclusion

Equipotential Bridging Bars unify separate earthing systems into a single, coordinated safety network.

By eliminating dangerous voltage gradients and managing transient surge impedance, they protect infrastructure and personnel during lightning and fault events.

When engineered in accordance with Australian standards and installed with robust isolation and termination accessories from SCHNAP Electric Products, they form the foundation of resilient electrical infrastructure.

In lightning protection engineering, unity of potential is unity of safety.