A massive power outage across most of Northland was entirely avoidable, a major report into the cause has found.
The Electricity Authority has just released its review into the collapse of the electricity transmission tower that left 88,000 in Northland without power in June.
The report found Transpower missed an opportunity to take action when staff raised concerns relating to training processes in 2021.
A senior engineer had then identified a gap in the knowledge of maintenance crews undertaking the foundation work and recommended Transpower organised new training sessions with all new crew members, and to do refresher training every 12 months.
"This wasn't acted on. The failure to respond to, or action, the concerns raised does not align with the principles of proactive risk management and continuous improvement that we would expect to see within Transpower," the report said.
"Although Transpower described the event as 'unprecedented and inconceivable', the underlying factors that contributed to the tower's collapse were entirely avoidable," the report found.
Energy minister Simeon Brown said Transpower's failure to act on these opportunities had led to terrible consequences for the people of Northland, and there was evidence the removal of all nuts from more than one tower leg was not a one-off event.
"These are incredibly concerning findings, and the report identifies a number of recommendations that I expect Transpower will fully accept and act with urgency to address," he said.
The report estimates the economic loss for Northland ranged between $37.5 to $80 million.
"A system that lacks training and supervision allows this to happen, so we think that is the cause," Independent chair Sarah Sinclair said.
"It also highlights the real opportunity around regional resilience and making for every region of New Zealand a more resilient electricity system."
Brown presented the findings on Wednesday, which come with 26 recommendations for Transpower, including improving its training for contractors.
"I will be writing to the Electricity Authority to express my expectation that the recommendations are implemented and that they work with Transpower on the implementation of the recommendations that are relevant to them."
In August an independent report found contractor error was to blame for the collapse of the power pylon in Auckland's Glorit.
The fallen pylon at Glorit after too many nuts were removed at the same time. Photo: Transpower
It said a relatively inexperienced and inadequately supervised worker removed nuts from three of the four legs of the pylon, compromising its stability and causing it to rupture and fall, cutting power for hours.
At the time of the outage, Energy Minister Simeon Brown ordered the Electricity Authority to review the cause.
In a statement issued by Transpower, executive general manager of grid delivery Mark Ryall said it acknowledged and accepted all of the recommendations of the report by the Electricity Authority.
"We accept the recommendations for Transpower in this report. They are generally in line with the recommendations already made in the report we commissioned, which was released last month. We are well underway with the actions in response to those recommendations and are updating our progress regularly on our website," he said.
When asked about compensation by RNZ's Midday Report, Ryall said it was not required to compensate impacted customers under the current rules.
Ryall said it would be impractical to have a 100 percent guarantee of power supply at all times, and that if that was a requirement - it would significantly increase the price to consumers in order to cover that risk.
The Electricity Authority's report said the issue of compensation was outside the scope of its review.
"While we recognise the importance of this issue to Northland consumers who have suffered significant losses because of the event, the Authority has no powers to order compensation," the report said.
The authority's chief executive, Sarah Gillies, said they were separately investigating an alleged breach of the Electricity Industry Participation Code, by Transpower, in its role as the grid owner.
She said the compliance process may allow for certain orders to be made by an independent ruling panel, however that process had not been completed yet.