The wait for some Aucklanders' electricity to be reconnected will enter its second week tomorrow after last Tuesday's gales caused widespread failures. The massive cuts recall the central city's five-week outage in 1998.

Twenty years ago, Aucklanders basked in a hot summer, only to have it plunge them into arguably the region's worst power cuts.

A series of faults in the city's electrical arteries left the heart of the city nearly powerless for five weeks in February and March 1998.

The CBD, dependent on its lifeblood of electricity for commerce, government and a growing number of apartment dwellers, was left with the comparatively feeble pulse of one underground cable and the noisy throb of smoky generators plonked on city streets.

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Even a cargo ship anchored in the city, the Union Rotorua, was roped in, its turbo-electric motor powering up the Ports of Auckland.

The CBD blackouts of two decades ago are considered the worst of five to have hit the city from 1998 to 2014; they were certainly the longest running.

The inner city was home to more than 7000 people at the time and 70,000 people worked there in several thousand businesses and government agencies. More than half of employers moved their operations out for the duration. Some went bankrupt.

Last Tuesday, after storms lashed Auckland with winds of more than 100km/h, cutting power in 150 outages, around 180,000 homes and businesses were left without electricity. By today, up to 1500 were still without electricity and/or hot water, in some cases due to trees continuing to fall on power lines.

In 1998 it was the opposite of a wintry storm: it was an El Nino summer. There was a drought and February was hot, fuelling electricity demand from CBD air conditioning.

This had a crippling effect on central Auckland's ageing power supply. The CBD was fed by four 110 kilo-volt underground main cables - one pair that were gas filled and dated from the 1940s and another pair of oil-filled cables from the 1970s - and a solo 22kV cable from Kingsland.

Hot, dry ground and heat changes in the cables caused movement and instability. Faults in the gas cables put more demand on the oil ones, which overheated and failed.

The first the public knew of the impending crisis was a message from the power supplier (then known as Mercury Energy but now called Vector) advising CBD customers to conserve electricity, otherwise "drastic measures" would be needed.

By that point, February 19, three of the main cables had failed. The first went out in January. The fourth failed on February 20, leaving the Kingsland thread as the power lifeline.

Lights went out, people were caught in lifts, air conditioning stopped, traffic signals were intermittent, food was spoiled, cash registers stopped ringing and retail and restaurant trade slumped by 90 per cent.

Before rationing was introduced, with rolling blackouts as power was shared around, the loss of electricity was intermittent and unpredictable.

Temporary, overhead, 110kV cables were strung up on concrete pylons hastily erected along the rail corridor into the central city. Finally, on March 27, the crisis was over, although power outages continued until May 1998.

A ministerial inquiry criticised Mercury Energy and its predecessor the Auckland Electric Power Board. Their management of the 110kV underground cables were "below industry practices". Mercury placed heavy reliance on the oil cables, but this was "unaccompanied by any investigation of their actual conditions".

A power supply tunnel, containing new cables, from Penrose to the CBD was completed in 2001, construction having started in 1997.

One of the results of the 1998 ministerial inquiry was that lines companies were required to publish their asset management plans.

Many shops in Auckland were forced to close by the June 2006 power cut. Photo / Martin Sykes
Many shops in Auckland were forced to close by the June 2006 power cut. Photo / Martin Sykes

Eight years later, in June 2006, it was the turn of half of the city to lose power. Ageing infrastructure and the weather were again at fault, but this time, rather than a complex, multi-layered cable, it was ridiculously simple: two rusted steel shackles on overhead earth wires.

The D-shaped connector shackles had broken in a 90km/h wind, allowing the wires to fall and make contact with a 220kV and 110kV conductors at the Otahuhu sub-station.

One of two rusty D-shackles that failed on earth wires at the Otahuhu sub-station in 2006, causing a massive power cut in Auckland.
One of two rusty D-shackles that failed on earth wires at the Otahuhu sub-station in 2006, causing a massive power cut in Auckland.
The fallen earth wire, one of two that caused a massive Auckland power cut in 2006, can be seen draped across high voltage lines at the Otahuhu sub-station.
The fallen earth wire, one of two that caused a massive Auckland power cut in 2006, can be seen draped across high voltage lines at the Otahuhu sub-station.

Power was cut to 230,000 customers - more than 700,000 people - in the CBD and in central and southern suburbs for six hours after the failure at 8.30am.

The disruption again included people being trapped in lifts. Around 300 traffic signals failed, trains stopped, and Auckland University of Technology closed its city campus.

Major Auckland power outages

• 1998 - The CBD suffered five weeks of blackouts after the failure of the four main underground cables, partly because of a hot summer.

• 2006 - The CBD and south and central suburbs lost power for six hours after two rusty, steel D-shackles failed at a sub-station in high winds.

• 2009 - Power cut for three hours to about 280,000 customers - all of Northland and the northern half of Auckland - after a forklift lifted a container into wires.

• 2011 - Around 200,000 northern and Auckland electricity users lost power for several hours after a fault in Transpower's connection to the Huntly power station.

• 2014 - More than 85,000 customers in Auckland's central and eastern suburbs lost power for more than 12 hours after a fire in a cable trench at Transpower's Penrose substation.

• 2018 - 180,000 Auckland customers left without power after damage caused by winds of more than 100km/h. Some have been waiting nearly a week to have power restored.