The lawyer who headed a probe into a previous Auckland power blackout says an inquiry into the most recent cut needs to look at reliability across the entire Auckland network.
Energy Minister Simon Bridges has asked the Electricity Authority to investigate Sunday's cut which left 85,000 homes and businesses without power, many of them for two days, after a cable fire at a substation in Penrose.
It was the latest in a long history of major black-outs in Auckland over the past two decades.
The most dramatic, in 1998, saw power knocked out to the entire central city for five weeks after four cables supplying electricity failed one by one.
That sparked a major inquiry into Auckland's power supply, led by lawyer Hugh Rennie.
Yesterday, Mr Rennie said that had prompted major changes, but the latest outage showed there were still gaps.
He said while the problem was at the Penrose substation, it would be disappointing if the inquiry only focused on that particular incident.
"A better inquiry would look at the systemic issues of reliability, risk management, infrastructure age, [and] quality of infrastructure management on a more general basis."
Mr Rennie said the inquiry didn't need to cost a fortune or run forever to achieve that.
"Perhaps one that sampled different points of the system so you could get a better perspective of how good the current situation is."
Ralph Matthes chairs the Major Electricity Users Group, which represents Fletcher Building, Rio Tinto, and other big power users in New Zealand.
He said he would also like to see the inquiry take a broad view of Auckland's network.
"It does make you ask the question, is there something peculiar about Vector? Is there something unusual about where it operates that makes these sorts of incidents perhaps more frequent? Again, I don't know, but that's an empirical question for the inquiry to look at."
Mr Matthes said the inquiry also needs to ask why power cuts are still happening, even after Vector and Transpower have ploughed hundreds of millions of dollars into upgrading the network.
"It may be something to do with the way that they ... identify the risks and manage it from an operational point of view, rather than actually requiring additional capital expenditure to gold plate it."
Energy Minister Simon Bridges said the inquiry's immediate focus would be what happened at the Penrose substation, but he appeared to leave the door open for bigger questions.
"It will be a relatively wide-ranging inquiry where they will be able to step back and understand what's gone on and what policy implications there are, more broadly speaking."
Mr Bridges said without pre-judging the inquiry, he didn't think the automatic conclusion would be to spend more on infrastructure.
"We'd want to be careful about that, because with all recommendations for more significant infrastructure spend, of course there's a cost and a price implication on electricity."
He said he expected work on the inquiry to begin today.
The Electricity Authority is due to report back by the end of April 2015.
Some without power in South Island
Meanwhile a small number of rural customers in south Canterbury and Otago will be without electricity until later today as companies repair power lines snapped in high winds overnight.
Power has been restored to customers from Omarama to Ohau, but about 15 farms between Twizel and Omarama will be without electricity until tonight.
Lines company Alpine Energy said customers in central Otago, near Alexandra had also lost power.