Auckland's blackout could have been avoided, inquiry finds

An independent report into Auckland's blackout on June 12 says more could have been done to ensure security of supply, Energy Minister David Parker said today.

The power cut was caused by the failure of two shackles holding up wires at the Otahuhu substation and the review makes four recommendations to reduce the risks of further power cuts in the short term.

The review, conducted by engineering firm Connell Wagner, said the Otahuhu substation had major and minor design deficiencies and there were "small, but critical weaknesses" in Transpower's maintenance programme.

It also warns of a need to review critical points in the entire national grid to reduce risks of similar blackouts elsewhere.

"Otahuhu is recognised as being an absolutely critical element of the grid, but we have found no evidence that Transpower has any special inspection and maintenance process to recognise that criticality," it said.

The failure of two 40-year-old shackles brought down an earth wire at the station on top of power lines causing them to short out, cutting power to much of Auckland for more than five hours.

The report said there was no evidence the shackles had been inspected in 2003. "If they had been inspected, their poor condition would have been obvious."

Inspections since the blackout had reduced the risk of further problems at Otahuhu, but the report recommended four short-term measures, including making incoming overhead earthwires more secure.

It also said moves should be taken to reduce the number of wires crossing over each other and, where this was not possible, implementing a special maintenance regime where they did cross.

This should include putting the existing 220kV circuits that cross over the 110kV portion of the substation underground.

The report said the short term measures would not solve longer term issues with the power supply into Auckland.

"The fundamental issue of too much dependence on Otahuhu will exist until a second major point of supply into Auckland is established."

The report said Mr Parker should consider Transpower's suggestion of a new "eastern corridor" power supply into Auckland "subject to (it) being environmentally and socially achievable".

Transpower has proposed using a new transmission line across the Waikato as a way of setting up a new route of supply into Auckland. However the proposals have been blocked by the Electricity Commissioner.

In a letter to Transpower, Mr Parker said he wanted to know by July 21 how long the SOE would take to finalise its views on the eastern corridor and other long term solutions.

Mr Parker also asked for a list of risk points around New Zealand, how bad they were "and what mitigation measures you already have planned."

- NZPA