Giant transformer goes underground

Meridian’s Manapouri Power Station has taken delivery of a new transformer that’ll give the hydro station a huge boost.

The 104-tonne transformer’s New Zealand journey took several days.

After arriving in Bluff from Australia, the 135MVA transformer was unloaded onto a trailer for the 170km road trip to Supply Bay, before barging across Lake Manapouri.

Items this large have previously used Deep Cove in Doubtful Sound and then been transported over Wilmot Pass, says Meridian.

Following the slow and scenic journey across Manapouri, the transformer was reversed down a two-kilometre road access tunnel into the machine hall.

“There were plenty of early starts and late finishes, but our Meridian team and suppliers have achieved an outstanding result for New Zealand’s electricity supply ahead of Winter ‘25,” says Meridian generation acting general manager Yanosh Irani.

“This has been months of work, planning, and coordination, and the specialist skills on display have been amazing – Meisters for barge operations, Move Logistics for transportation from Bluff to Supply Bay and then again at West Arm, and E-Type for fabricating and installing two unloading wedges for the delivery.

“A real – and world class – team effort.”

Manapouri Power Station has been operating at reduced capacity for about two years, following faults in two of its seven transformers, so the arrival of the first replacement transformer is considered a major milestone.

“We saw this winter just how important every single megawatt is, so this transformer has landed at a brilliant time,” says Irani.

“Getting our biggest power station closer to full capacity will boost security of electricity supply next winter and, in the meantime, give us the ability to ease off generation in the Waitaki to help restore storage levels in Lake Pukaki.”

The new transformer will increase generation capacity at Manapouri from a restricted limit of 640MW to about 768MW – close to the maximum 800MW allowed under consent conditions.

Work to commission the new transformer is expected to be completed by Christmas this year with the second replacement transformer (along with a spare) due to arrive in late 2025.