The Court of Appeal has upheld a decision by the Electricity Commission to approve an upgrade of Transpower's substation in Otahuhu, Auckland.
Judicial review proceedings were initiated by the Major Electricity Users' Group, which claimed the commission violated electricity governance rules.
The upgrade is intended to improve the reliability of the power supply to Auckland and Northland, following a blackout in Auckland in 2006.
The plan was unsuccessfully challenged by the Major Electricity Users Group in the High Court.
The group then tried to appeal its case, but the Court of Appeal found no error in the analysis used by the commission.