"We apologise to the communities affected for the disruption," he said.
No further details on what the error was have been provided.
Once they knew there was no risk to safety, the supply was able to be restored.
The outage was centred at the Kikiwa substation 110kV bus, near Nelson. Around 30MW was lost.
"Fortunately, with crews on site at Kikiwa we were able to restore load reasonably quickly, with our load restored by 10.45am to the local lines' companies, who took about another 1 hour to have everyone back on."
At the time, Hits presenter Dave Nicholas was on holiday staying at a bach in Fox River, between Greymouth and Westport.
"I was just chilling out, going with the flow of the morning and then everything went dark.
"It's a little bit frustrating, I'm already in a primitive area as it is. The electricity was quite a bonus, quite a luxury, but now it's not there anymore," he said.
Nicholas said it is concerning that the two major lines on the West Coast can go down.
"It leaves the region sort of hanging by a thread. A little bit concerning, I don't know how often this happens."
