Power pylon problems: New line to Coromandel alone could cost $500 million

The downed pylon near Kaipara in June, which toppled after too many nuts were loosened. Photo / Michael Craig

The huge cost of getting new power lines to improve energy security in places such as Northland and Coromandel has been outlined in official documents about the Glorit power pylon debacle.

The pylon with too many loose nuts toppled in June, knocking out power to almost 100,000 people and putting infrastructure in the spotlight.

Documents released to the Herald under the Official Information Act (OIA) showed officials expected to be asked about redundancy and energy security in the regions.

Papers prepared for Energy Minister Simeon Brown and other correspondence indicated getting a new line to the Coromandel would cost $500 million.

“Under the current transmission pricing methodology that cost would fall fully on the 25,000 connections in the Coromandel – a cost of around $20,000 per connection,” Transpower head of communications Diana Price said in an email among several updates prepared for Brown.

The tower that toppled at Glorit, pictured in a photo released to the Herald under the Official Information Act. Photo / Supplied

Labour’s energy spokeswoman Megan Woods said the transmission pricing methodology referred to was two decades in the making.

She said the Labour Government had tried working on issues related to resilience and more distributed generation, and increasingly extreme weather and more demand for electricity made this planning important.

“What could we be doing at the community level? We had funding under the Climate Energy Response Fund but that was cut.”

At $20,000 a connection for the Coromandel line, it’d probably be cheaper for households and businesses to install their own solar systems.

Labour's energy spokeswoman Megan Woods says events such as Cyclone Gabrielle show the need for more resilience in infrastructure.

On whether solar panels should be installed on high-quality agricultural land, Woods said it depended on the context, and structure of the solar array.

“Obviously we do not want to cover our high-quality soils in solar panels.”

But Woods said some solar installations were set up to allow agriculture to continue around or beneath them.

A key struggle for energy resilience was the skinny geographical profile of New Zealand. The national grid, which Transpower owns, is often just one line running north to south.

Two lines and sets of towers feed Northland – one for 110kV and the other 220kV, documents from Transpower said.

Each of the towers carried two circuits and each circuit was multiple pieces of wire.

Loose units: The falling pylon of Glorit caused massive inconvenience and sparked new questions about the power network's resilience. Photo / Supplied

“One of the 220kV circuits was out for maintenance and the other was in operation,” Price of Transpower said in the OIA documents.

“Both 110kV circuits were in operation but were reconfigured to protect the assets should the 220kV circuit that was in operation trip. This reconfiguration had no impact on supply to consumers, and is standard practice.”

The documents discussed how redundancy did exist in the system, with most regions having something called n-1 security.

“This means that if something happens to a circuit or transformer there is another that can take the load,” Price told the minister’s office and others copied in.

“To ensure that the power system is in good working order we do need to remove circuits and transformers from service from time to time to conduct maintenance, asset replacements, and upgrades.

“Having that equipment out of service means reduced security. For most regions that means if something happens during that time to the remaining transformer or line there is a loss of supply to consumers,” Price added.

Megan Woods said the high cost of getting new lines to sparsely-populated regions is partly the result of very old pricing systems. Photo / Alex Cairns

“This is standard procedure and we work as quickly as we can to restore either the equipment out for maintenance or the equipment with the issue and return power to consumers,and forms part of the planning for the work.”

The documents released to the Herald showed Transpower was mulling what consequences contractors Omexom would face.

“We have raised our concerns with Omexom senior management in New Zealand and Singapore,” Price wrote to Brown’s office and other recipients on June 23.

Transpower on August 1 said the tower fell because the Omexom crew who were performing routine baseplate maintenance work did not follow Omexom’s standard practice and removed all the nuts from three of the tower’s four legs.

It said the less-experienced workers received some training but not any formal training for the work they were doing, and were not certified by Omexom as competent for the tasks they completed unsupervised.

Transpower told the Herald it reviewed Omexon’s performance across all the work completed over the past two years.

“Senior members of Omexom appeared before the board in June and were asked to reappear in late August to outline the recommendations and actions from the reviews, and detail their improvement programme.”

Transpower added: “We are confident that Omexom is working hard on addressing the issues that led to the tower fall to ensure something like that never happens again.”