Blackout report says maintenance system failed

The Otahuhu substation where the failure of a shackle left Auckland without power. Picture / Richard Robinson

A report identifying the cause of Auckland's power blackout is believed to show that maintenance checks failed to pick up a faulty shackle.

Energy Minister David Parker received the report from Transpower on Friday and it is due for release today. Late yesterday the minister was going back to the national grid operator for more data on maintenance.

The report was discussed at a Cabinet meeting yesterday, and Prime Minister Helen Clark later said that in her view it "does substantially make it clear" what was to blame for the blackout. She would not elaborate before the release of the document.

Auckland lost its power during a storm just over two weeks ago, when a simple metal shackle holding an Otahuhu substation earthing wire failed and the wire snapped. Part of the wire fell into switching equipment and the resulting blackout lasted all day.

Sources yesterday indicated that the D-shackle which failed might have been rusty, but its condition was not spotted during Transpower's usual checks. Transpower has already said maintenance was running to schedule.

The Government wants to move quickly to ensure the failure is not repeated, but it is also keen to make sure it has comprehensive knowledge of what happened and how to fix it.

Transpower's report into the blackout is not the only information the Government has requested or received. It was accompanied by an independent version of events commissioned by Transpower, and the Government has also appointed an independent party to review all the documents.

Mr Parker said consultants from Connell Wagner in Australia were expected in New Zealand yesterday to review Transpower's report. That review is due by July 6.