Auckland's power hangs by a thread

One of the broken earth wires which triggered yesterday's power chaos. Picture / Richard Robinson

National electricity grid operator Transpower was under fire from political, business and civic leaders last night over the huge power cut that brought chaos to Auckland yesterday.

The cause was a small earth wire which a wind gust snapped off a high-voltage pylon near the Otahuhu B substation, short-circuiting lines supplying electricity for 700,000 or more people throughout central, east and southwest Auckland.

Prime Minister Helen Clark was among those who questioned the city's reliance on a single gateway substation between Otara and Otahuhu, saying the Government would seek answers from Transpower.

Four loud bangs heard by road builders several hundred metres away at 8.32am signalled a day of disruption not only to the main 220,000-volt power feed to Auckland's central business district, but also to three of line company Vector's local substations.

The earth wire, designed to protect pylons from lightning strikes, flicked off the main link and on to 110,000-volt switching equipment at Transpower's Auckland gateway substation.

That cut all the substation's output, and also threw the Otahuhu B and Southdown generating stations off the national grid.

A second 220,000-volt line running power to Waitakere, North Shore and Northland was undamaged, letting Transpower feed some load back to central Auckland by late morning, although it took until after 4pm to restore supplies to the rest of the region.

Vector, which receives bulk supply from Transpower, had to take care to restore electricity gradually for safety reasons after separate lines feeding 55,000 customers fell in storm conditions.

'Traffic lunacy' after 300 traffic lights disabled

Commuters faced what the police called "traffic lunacy" after 300 sets of intersection lights were knocked out of action, thousands of workers were left with little to do in darkened offices and factories, shops were shut and university exams cancelled.

Some schools also closed and sent children back early to darkened homes.

Despite some minor collisions and near-hits, the police were thankful nobody was seriously injured in Auckland, although a Chinese sailor was swept off an oil tanker in heavy swells off Wellington as big seas and gales swept up from a snow-blanketed South Island.

Winds also gusted to 80km/h at Auckland Airport and to 130km/h in the outer Hauraki Gulf as contractors scaled the stricken 40m power pylon to secure the two ends of the snapped earth wire.

About 2000 households and businesses also lost power at various times in the Waikato, but lines company WEL Networks said that was from storm damage unrelated to the Transpower disruption.

Auckland City and Middlemore Hospitals had to switch to emergency generators, and sewage pumping stations began overflowing into Waitemata Harbour by mid-afternoon.

That brought an appeal from Auckland City Council for householders not to wash clothes or dishes, and to flush toilets only when absolutely necessary.

Before power was restored to most areas from about 12.30pm, dozens of motorists milled around some service stations with empty petrol tanks, unable to refill their vehicles from electrically operated pumps.

For the first time since its opening on Thursday, the Sylvia Park mega-shopping mall had plenty of spare parking spaces, as The Warehouse Extra waited in darkness for an emergency generator to arrive on the back of a truck snarled in heavy motorway traffic.

The disruption drew heated reactions from Auckland City Mayor Dick Hubbard and business leaders, who fear millions of dollars of commercial losses.

Helen Clark said the blackout was "not a satisfactory situation" and Energy Minister David Parker asked Transpower to investigate separating out parts of the Otahuhu substation under its plan to upgrade transmission into Auckland after 2013.

Mr Hubbard said he was "very, very angry" that Transpower had allowed Auckland to be so dependent on a single substation, and he accused the grid operator of fobbing him off when he voiced concern about this some months ago.

"They said I was scaremongering for raising questions about the security of supply," said the mayor, who had to conduct a citizenship ceremony for several hundred immigrants in a darkened Town Hall and then had to explain the disruption to a Spanish tourism delegation.

Northern Employers and Manufacturers Association chief executive Alasdair Thompson, whose members were battered with the rest of central Auckland during weeks of power cuts in 1998, feared the disruption would reduce the region's attractiveness to investors.

"If it only takes a 110KV failure to take out a good slice of Auckland, then quite frankly, Heaven help us," he said.

Warning sounded after 1998 crisis

Energy consultant Bryan Leyland said he sounded a warning after a $70 million power cable tunnel was completed between Penrose and central Auckland after the 1998 crisis that the region's weakest link was to the south.

His call then for the link between Otahuhu and Penrose to be duplicated went unheeded and he believed it could still be built by upgrading a smaller detour line around Pakuranga for probably little more than the cost of yesterday's disruption.

Transpower spokesman Chris Roberts acknowledged there had been little new investment in the national grid for the past 20 years but his organisation was considering such an idea among various upgrading options.

Transpower had not experienced such serious disruption since becoming a state-owned enterprise 12 years ago, and the 1998 cuts were not of its making.

"We are devastated by this sort of event. Our goal all the time is to maintain reliable supply but we can never guarantee supply. No system is 100 per cent secure, no system anywhere in the world."

Mr Roberts acknowledged that the Otahuhu substation was several decades old but it was well-maintained, although the condition of the failed equipment had yet to be checked.

He said a new 400,000 volt transmission line which Transpower has been battling Waikato and South Auckland landowners to run from the central North Island would feed into a separate part of the Otahuhu substation.

Electricity Commission chairman Roy Hemmingway said his organisation would work with Transpower to investigate the cause of the disruption to decide whether investments were needed to guard against any recurrence.

Auckland was probably more dependent than most cities on a single gateway substation, largely because of the region's geography.

- Additional reporting by Simon O'Rourke and Paula Oliver