The project addressed the replacement of ageing NAB1 air circuit breakers that had reached end-of-life, creating increased reliability risks, safety concerns, and difficulties sourcing spare parts.
Traditional replacement methods would have required extensive switchboard modifications, prolonged shutdowns, and significant production impacts. To overcome these challenges, Nilsen developed a fully engineered retrofit system that integrated modern circuit breaker technology into the existing switchboard infrastructure while maintaining the original footprint, busbar alignment, and operational configuration.
The innovation centred on a modular retrofit architecture designed specifically for legacy NAB1 breaker installations. Each assembly incorporated custom mechanical interfaces, purpose-designed copper busbar connections, and integrated secondary contact systems, eliminating the need for major structural switchboard modifications. The solution was manufactured, assembled, and tested off-site before installation, significantly reducing outage durations and site-based work.
A key advantage of the design was its “plug-and-play” installation approach, enabling efficient deployment within limited shutdown windows. Existing infrastructure components were incorporated where practical, simplifying installation while minimising disruption to ongoing smelter operations.
The retrofit assemblies incorporated Schneider MTZ air circuit breakers with Micrologic protection systems, delivering enhanced fault detection, improved discrimination, advanced monitoring capability, and increased system reliability. Safety was also enhanced by reducing reliance on ageing equipment and minimising manual intervention during operation and maintenance activities.
A significant feature of the project was the rigorous independent performance validation undertaken to demonstrate the suitability of the retrofit design. Temperature rise testing was conducted across multiple current ratings, including 1600A, 2000A, 2500A, and 3000A, in accordance with Australian standards for low-voltage switchgear assemblies. Testing confirmed compliance with temperature rise limits, stability of custom busbar interfaces, and suitability for continuous full-load operation. This independent verification demonstrated that the solution was a purpose-engineered product rather than an adaptation of existing equipment.
The project progressed through detailed site investigations, engineering design, manufacturing, assembly, testing, and staged deployment aligned with operational shutdown requirements. Challenges relating to legacy equipment tolerances, thermal performance, and secondary contact integration were resolved through iterative design development and validation testing.
Beyond the immediate project, the retrofit solution has created a scalable model for modernising ageing switchboard infrastructure across a wide range of industrial facilities. The approach can be adapted to other NAB1 installations and similar legacy systems, providing asset owners with a cost-effective alternative to full switchboard replacement.
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From large-scale infrastructure to tailored electrical solutions, reach out to our team today to find out how we can support your project.
