The fault that cut electricity to thousands of Christchurch customers last week was probably caused by debris hitting key equipment at a power sub-station.
Some 30,000 customers lost power on the night of 9 July, some for three-and-a-half hours.
Rob Jamieson, chief executive of lines company Orion, said on Monday that debris appears to have hit high voltage equipment at the Papanui sub-station and exploded on impact.
The fault serves as a reminder for people to be prepared for an outage or emergency event, he said.
