Medium Voltage Bus Systems

Isolated Phase Bus Duct Systems

Safe, reliable electrical bus systems to meet medium- and high-voltage demands in multiple generation applications

Innovative isolated phase bus duct systems to meet global demands

Around the world, AZZ’s medium voltage bus duct systems are found in a wide range of critical applications that demand the highest degree of reliability. For decades, plants and facilities have counted on AZZ’s knowledge and expertise in custom-designed solutions to deliver unmatched performance in isolated phase bus ducts.

Deployed as generator main leads extending to GSU transformers and excitation service/auxiliary transformers, AZZ isolated phase bus systems are a cost-effective, fully integrated option for multiple applications:

  • Hydro plants
  • Nuclear power stations
  • Combined cycle power plants
  • Fossil plants
  • Renewable plants 

The advantages of a value-based partner

As a single-source provider, AZZ can provide opportunities for cost efficiency not available with other bus system suppliers. Our elbows and t-taps are welded in-plant and are easier to install, reducing costs in the field. Our extensive shipping capabilities include transporting 40-foot sections with all three phases shipped on a single skid to also lower field costs.

Engineered for optimal performance

With AZZ’s advanced design, each phase is mounted in individual enclosures, with conductors that are air insulated and supported in the center phase enclosures by strategically arranged insulators. This safer approach delivers maximum system integrity that eliminates phase-to-phase short circuits, while our insulated saddle supports prevent current from being induced in the steelwork, cables, pipes or other metal structures.   AZZ can design and install the entire system, including interfaces with major manufacturers of generators, generator circuit breakers and transformers.


isolated phase bus, AZZ


  • Current: 600–25,000 (air cooled)
  • Up to 50,000 amps (forced-air cooled)
  • Voltage: 15kV–38kV
  • Insulation levels: 110–200kV (BIL)
  • Momentary current: Up to 1,000,000+ Amps Asymmetrical
  • Meets or exceeds ANSI/IEEE and IEC Standards

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