IEC 60105: Commercial Aluminium Busbar Material — The Arteries of Substations and Switchgear

Aluminium Busbars — The Arteries of Switchgear and Substations

IEC 60105 specifies commercial-purity aluminium busbar material. In substations and large switchgear, busbars carry thousands of amps continuously and tens of kiloamps under fault — aluminium is the cost-optimal choice.

Key design parameters: (1) Ampacity — Al busbar ampacity is ~80% of equivalent Cu cross-section. But Al density is only 30% of Cu — for equal conductance, Al weighs half as much and material cost is ~1/3. (2) Contact resistance — Aluminium rapidly oxidizes, forming a high-resistance Al₂O₃ film. Busbar joint surfaces must be silver- or tin-plated, with bolted contact pressure ≥20 MPa to break through the oxide film.

TN Lab — An unplated aluminium busbar joint can have 10× the designed contact resistance.