MainPower’s sub-transmission line between Oaro and Cheviot is constructed at 66 kV but is currently operating at 33 kV. This major project will shift the 66/33 kV transformer from Cheviot to Oaro, allowing the line to operate at 66 kV.
Land has been purchased for the relocation of the Oaro Zone Substation to a new site where the new 66/33 kV transformer will be located.
Why are we undertaking this work and what does this mean for our customers?
Upgrading the sub-transmission line from 33 kV to a 66 kV will help with the current population growth of the area and support capacity growth stability within the surrounding areas. As the number of customers on our network grows, the network must grow with it. By proactively increasing the sub-transmission line capacity, we are prepared for future demand growth and increased network resilience.
Current status (December 2025)
- Oaro Zone Substation: Concept design is complete; detailed design is progressing in step with the Kaikōura Zone Substation works.
- Kaikōura Zone Substation: Construction is planned to begin in 2026 as part of the staged upgrade path.
- Raramai Tunnel section: Foundations for new steel poles have been laid; erection of the poles is scheduled post‑winter as part of the coastal line resilience works.
- Programme integration: The upgrade is part of MainPower’s long‑term 66 kV strategy and sits alongside other Kaikōura reinforcement projects to address local constraints.
Timeline
- FY24–FY27: Cheviot to Kaikōura 66 kV line upgrade works, Oaro relocation and rebuild, Raramai Tunnel structure replacement, new 66 kV bay at Kaikōura.
- 2026: Line upgrade completion target and Kaikōura Substation construction start.
- Phase One Kaikōura Substation: Estimated completion 2028.
- Phase Two Kaikōura Substation: Estimated completion 2032, with consolidation of operations and retirement of Ludstone Substation.
