Auckland's fifth major outage since 1998 — Key warns network upgrade would hit consumers

UPDATED 4PM: The latest major power cut in Auckland is the fifth to hit the region since 1998.

The biggest was the six-week Mercury power outage in 1998 that involved the failure of four power cables due to overheating. It had an estimated long-term economic impact equivalent to 0.1 to 0.3 per cent of New Zealand's gross domestic product and over half of businesses within the central business district were forced to move out at least temporarily. 

Then in June 2006, a failure in a couple of shackles at the Otahuhu sub-station caused a six-hour blackout that had an impact on 230,000 customers and disrupted everything from rail services to radio transmissions and led to partial hospital closures.

In 2009, there was a power cut to some 230,000 customers in Auckland and Northland that led to the Marsden Point oil refinery being temporarily shut down. The outage was caused by a forklift driver lifting a shipping container into one of two high-voltages circuits while the other one was already out for maintenance.

And in 2011, Transpower's power system connection to the Huntly power station affected some 200,000 northern and Auckland electricity users  The power was off for several hours forcing businesses to close in the busy pre-Christmas period until reserve generation was brought online through other distribution companies. 

The outage that took out 85,000 connections was caused by a fire in a cable trench on at the Penrose sub-station in east Auckland, a site shared by the local network owner Vector and the national grid operator, Transpower.

At this stage, it's not clear where responsibility for the fire lies, although Vector has confirmed its assets were damaged rather than Transpower's.

Prime Minister John Key has suggested an inquiry may be in order to establish whether further redundancy should be built into the Auckland electricity network, although he warned today that any such investment would inevitably become a cost to consumers, reflected in the cost of electricity.

(BusinessDesk)

Fire safety investigators probe cause of Auckland substation power outage

EARLIER / 10AM:Fire safety investigators are at the site of the big power outage in Auckland today looking into the cause of the blaze that cut power to around 85,000 businesses and households over the weekend.

Lines company Vector said work is progressing well on the fire-damaged cables at the Penrose substation with all available crews working on repairing and reinstating them and it hopes to have power restored to everyone by 5am tomorrow. Customers in restored areas are also being asked to conserve power as much as possible so Vector can back feed more areas.

Assistant Area Fire Commander Dave Woon said it could take up to two weeks to report on the cause of the blaze which took four hours to bring under control in the early hours of Sunday morning. It was one of the more difficult blazes the Fire Service has had to work on, particularly as firefighters had to wait around an hour to ensure the power at the major substation was completely isolated and they would be safe to approach the trench.

By that time oil pressure pumped into the cables had seeped throughout the trench, fanning the flames and causing an intense heat to build up. Foam was used to knock back the flames so firefighters could access the 1.5 metre deep trench but Woon said it then took some time to remove heavy concrete tiles covering the cables before a heavier foam could be used to suffocate the flames.

"It was dark and smoky and that was a hard job. I had 35 people there working with the foam and tiles and this was a very technical job, not something we do every day. But we had a good outcome," he said.

The substation is owned and managed by state-owned Transpower which transfers the electricity on high-powered lines before lines company Vector then distributes it from the substation on its own cables throughout the suburbs.

Transpower spokesman Geoff Wishart said the cables were sitting above ground rather than being completely buried as they would at other substations around the country because the volcanic earth in that area affects the rating on the cable when buried - meaning less power gets through. He denied the problem was related to the age of the substation which he likened to George Washington's axe. "How many handles and how many heads can you replace on the axe before it is no longer George Washington's axe? This substation has had a lot of replacements in recent years."

There has been around $20 million spent on upgrading the substation, as part of a wider investment to improve security of power supply in Auckland. The $473 million North Auckland and Northland project which came into commercial operation in February provided a new 220kv cable from Pakuranga to Albany supported by two new substations at Wairau Road and Hobson Street.

The work gave an alternative route to move power through and around Auckland rather than relying on the single transmission line between Otahuhu and Henderson. Wishart said the current power outage from the substation fire would have been much worse and would have cut power to Auckland's central business district without the new cable.

Energy analyst Bryan Leyland said one of the key learnings from the substation outage was the need for better fire protection at substations across the national grid. Leyland said the outage highlighted something that was not looked at sufficiently by Transpower. "Cable fires are dangerous and people don't take the possibility of them sufficiently seriously because they are very unusual," he said.

Wishart said it was still not clear what caused the blaze and Transpower would investigate whether it needed to do anything differently in future around fire protection. Prime Minister John Key said there would be an independent inquiry into the blaze.

Fletcher Building, the country's biggest listed company, said its manufacturing and distribution facilities in east Auckland were disrupted by the fire, and is working with customers to minimise the impact. It doesn't expect the fire will have material impact on its 2015 earnings.

(BusinessDesk)