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.