There was no way to guard against a power spike which plunged Saturday's rugby test in Wellington into darkness, the stadium's management says.
A power failure during the test between the All Blacks and Argentina led to a nearly 30-minute, halftime break before the Westpac stadium's tower lights powered back up.
Yesterday, stadium marketing manager Steven Thompson said the outage was embarrassing but unavoidable.
"But in terms of the emergency systems working, everything worked to the way it should have been."
He said a power spike in the Wellington region took the main floodlights at the stadium offline momentarily.
Emergency lights at the stadium kicked in straight away, but the main floodlights took more time to bring back, Mr Thompson said.
"They need to cool down before they get back to operating temperature. And that takes several minutes."
He said it wasn't plausible to have the stadium's own back-up generator supply power to the floodlights in case the main supply cut out.
Transpower spokeswoman Rebecca Wilson said the surge was caused by a fault on a transmission line running into Wellington.
Engineers had checked the line yesterday and found no damage.
The fault - probably caused by high winds - cut power for a fraction of a second and would have caused a flicker of the lightbulbs in most homes.
"I think largely the length of the outage was because of the type of lights they have at the stadium."
Mr Thompson said the fact the outage came at halftime and not when the All Blacks were running for the tryline was a relief.
Match manager Dan Tatham, of the rugby union, said the organisation, stadium and host union planned for such problems. "As is our usual practice, we will review our operation around the test match, but we are satisfied that the contingency for the power failure ... was effective and smooth."
- additional reporting APNZ