The Dargaville and Maungatapere substation upgrades are major infrastructure investments supporting the integration of renewable generation into Northpower’s network. With the Mercury’s Kaiwaikawe wind farm and Northpower’s Puna Komaru solar farm set to connect into the system, both substations are being upgraded to manage higher power flows and strengthen network resilience across Northland.

Enabling the safe connection of new wind generation, the substation upgrades will improve long‑term reliability and capacity for communities across the region.

The project includes construction of a new overhead line and cabling to directly connect the Kaiwaikawe wind farm to the Dargaville zone substation. To accommodate increased generation and power flows, both Dargaville and Maungatapere substations are being upgraded to operate at 66kV.

At Dargaville, the existing two 15MVA transformers are being replaced with new 20MVA units. The switchyard has been extended to accommodate the larger transformers and a new dedicated 66kV bay for the Kaiwaikawe wind farm connection. Works also include upgrades to circuit breakers, voltage transformers, isolators, protection systems and auxiliary infrastructure.

Temporary network reconfigurations were required during construction, including the relocation of one transformer to allow for the movement of an 18.5‑metre concrete pole for the transmission line. The transformer was re‑established promptly to maintain N‑1 security, ensuring reliable supply throughout the works.

Given the scale of the rebuild, significant civil works were required at Dargaville, including redesigning the substation footprint and constructing new foundations while keeping existing equipment in service. A carefully staged approach allowed the substation to operate in a split‑bus configuration during the transition, maintaining reliability while new 66kV equipment was integrated.

At Maungatapere, the substation is being converted from a 50kV to a 66kV switchyard. Existing transformers were installed with future conversion in mind and are being upgraded through tap changes and the installation of additional equipment, including transformer fans, new voltage transformers, isolators and surge arrestors.