An investigation is underway into a major blackout that hit the Alice Springs area, with union officials saying the outage could have been avoided.
Power was cut across the central desert region at 2.18pm on Sunday with some services not restored for more than eight hours.
However, Territory Generation said power was restored to critical infrastructure, including the Alice Springs Hospital, within 30 minutes.
The government-owned corporation said it was investigating the cause of the blackout and could not provide further information at this stage.
But the Electrical Trades Union questioned the Territory Generation's handling of the transition of supply from the ageing Ron Goodin Power Station to the new Owen Springs Power Station.
"The guys on the front line live and breathe this stuff and they have been saying for months that Ron Goodin Power Station was prematurely closed and that Owen Springs was not adequately tested to ensure continuity of supply," union organiser Dave Hayes said.
Territory Generation had been urged by workers to keep the older power plant on active standby but their requests had been denied, Mr Hayes said.
He also called for an ETU member to be included on the government's official investigation team.
Northern Territory Essential Services Minister Dale Wakefield said the "system black event" on Sunday was unacceptable.
"Territorians deserve a stable and secure power system, and that is why I have called for an independent review into this incident," Ms Wakefield said on Monday.
"The independent review will identify and investigate any system-wide issues that led to this problem occurring and the adequacy of responses, both short and long term."
Australian Associated Press