It is likely that the Tiwai announcement sped the process up a bit. The upgrade was planned around the time that Meridian were planning Project Hayes. There were public meetings at the time in Alexandra and Ranfurly to discuss the impact on land owners along the route. The first stage of the upgrade took 2 years and involved duplexing the line between Roxburgh and Clyde, and thermal tensioning of the line between Clyde and Twizel. This was completed about 3 years ago. A change in the protection system at Roxburgh allowed a further increase in the power transfer north from Roxburgh. Duplexing the Clyde - Twizel circuits was always planned for 2021 and the duplexing of the Roxburgh - Naseby - Livingston circuit was to be the final stage in around 3 years time.
The reasons for the upgrade were because of the new wind farms planned for Otago. Even though Project Hayes was cancelled, the Mahinerangi wind farm has already completed stage 1, but the next 2 stages cannot go ahead until there is sufficient transmission capability. Add in Kaiwera Downs wind farm and that is a lot of energy to try and get out of the lower South. With Tiwai closing it is likely to delay Mahinerangi even further unless Onslow gets built.
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