How and why a "perfect storm" forced Emergency Department staff to use torches while treating patients last month, after Hawke's Bay Hospital's back-up power supply failed to compensate for a faulty switch, is still being investigated.
Some parts of the hospital were without power for 30 minutes between 11.45am and 1.04pm on March 23 as the hospital's three generators were inconsistent in delivering back-up electricity.
Failed components from an automatic switch have been sent to Germany "for further analysis and diagnosis", Unison customer care manager Danny Gough said. "What we are trying to uncover is what caused this extraordinary event to happen - a perfect storm," he said.
The switch to the back-up generators was still in place and could be operated manually.
"We are very comfortable for the security of supply and we don't expect any issues to kick in."