Speaking at a media press conference in Whangārei, Brown said he had visited the site of the fallen pylon and said "getting answers to what happened is a top priority".
The fallen pylon cut power to 100,000 properties on Thursday.
"It is completely unacceptable what happened yesterday, a pylon should not just fall down, that is something that should not happen in New Zealand outside of a major type of event.
"We need to get to the bottom of what happened, understand the facts. There needs to be accountability for that and appropriate actions to follow those reviews."
"It should not happen and we need to make sure it does not happen again."
Brown said Transpower had also started their own internal investigation and the government were currently considering whether to stand up an independent inquiry.
Transpower's executive general manager for grid delivery Mark Ryall confirmed the pylon collapse was an "isolated incident" and they were "not concerned about another tower".
Brown said if "all things going well" the temporary structure being brought in to fully restore power into Northland would be running by Saturday evening.
"Fortunately the site is very close to the road which makes it a lot easier to access, get equipment onto, which I think makes [Transpower's] job a lot easier."
Ryall said at the moment their 110 kilovolt circuit was still distributing power into Northland and it was asking locals to conserve electricity during peak times.
"We just apologise for the inconvenience of people losing power yesterday and for anyone who still has issues today. It is unacceptable, a pylon shouldn't just fall down," he said.
Transpower wanted to learn from this experience as well, he said.
"We will be honest and open with that review and we want to learn as well because we don't want this to happen.
"We pride ourselves in the performance of our grid."
In a statement, the Electricity Authority confirmed it was undertaking a review.
"Minister for Energy Simeon Brown requested the authority carry out a review under Section 18 of the Electricity Industry Act 2010 after the collapse of a transmission tower cut power to consumers in the region.
"As the regulator, the authority is best placed to conduct an independent investigation into the events and welcomes the opportunity carry out a review."
Chief executive Sarah Gillies said consumers needed to be confident their electricity supply was as reliable as possible.
"Or review will seek that assurance on behalf of consumers.
"Interruptions to the supply of power do occasionally happen, but we want the New Zealand public, especially those in Northland who were left without power, to know that we are intent on getting to the bottom of the problem and making sure any issues identified are urgently corrected.
"Northland consumers have been significantly impacted, including businesses that can't power their operations, process payments or have been forced to work in the dark. They deserve answers, and they need to be assured that this won't happen again."
Gillies said it would work closely with Transpower, local lines companies and other agencies during the review.
Gaps found after Cyclone Gabrielle come up again
Mayors in Northland said they have been assured by government and Transpower that the fallen pylon is a "once-off" situation.
"We as a mayoral forum are incredibly satisfied that we know, with certainty, with the Minister for Energy here himself, that we will see the restoration of business as usual by next week, just in time for the re-opening of our gateway, SH1 at the Brynderwyns, so everybody, nau mai haere mai ... get up here and spend your money, we definitely need it," said Far North mayor Moko Tepania.
"In terms of the longer term planning though, that's where all of these learnings and these lessons have to come into play."
He said Cyclone Gabrielle highlighted that the region needed resilience in transport, communication and power.
"Yesterday, we saw all three of those fail again."
Tepania said they were looking to working with central government to ensure an situation like that "never happened again".
The "saving grace" they had in this instance was an investment into the Ngāwhā Geothermal power station by their local lines company Top Energy, he said.
"Without that investment, Northland would have been dark last night so that investment and that foresight and that planning that happened decades ago to see that plant open up has paid off in spades."
Whangārei Mayor Vince Cocurullo said they had received assurance from the Brown and Transpower that this was a "once-off" situation.
He said they were currently in the process of talks for more investment in Northland.
RNZ
