"The level of instantaneous reserves being scheduled may or will be reduced".
Genesis says it has responded with all generation capacity within its control. At the time of the Transpower notice the company had all planned generation in the market for this evening, which includes all hydro, wind and gas generation.
Earlier today Transpower told customers there was a problem with the interisland power link.
It said there was an unplanned outage of HVDC Pole 2 due to a tower arm failure.
A conductor (wire) has fallen from a tower around State Highway 7 in the Weka Pass area, Waikari in North Canterbury, the statement said.
''Crews are onsite assessing damage and planning for repairs."
"The market is currently stable however, if there is a major plant failure, there is a risk of not being able to meet demand through the evening.
"We are approaching generators requesting more generation now. We have asked electricity distribution businesses (lines companies) in the North Island to reduce all controllable demand (such as hot water)."
During today's 6.10pm Covid update, it was confirmed the Transpower grid notice resulted from a conductor wire falling in North Canterbury. Nobody was harmed.
It reduced almost by half the amount of power that was able to come across the Cook Strait.
Generators had brought on more power, for this evening the situation appeared to be stable, Robertson said.
There were crews on site tonight to repair the wire. But it was work requiring daylight.
They hoped to repair within a day, or at most two days.
There was always an evening peak and with everyone home tomorrow there would likely be a higher use during the day too. Grant Robertson said he was confident enough had been done to manage this increase workload.
Counties Energy earlier sent an urgent message to its customers on Facebook, warning of potential power loss.
"Please prepare for potential loss of power. We will keep you updated as soon as we know more," the company said.
The Electricity Authority is already investigating last Monday night's blackout. That investigation will centre on Transpower's role in outages that left 35,000 consumers in the dark on the coldest night of the year.
The initial phase of what will be a wider review of the industry will centre on whether Transpower systems were up to scratch. The role of lines companies and generators will be investigated in a later, wider review.
An initial report into the blackout will be made public and the authority says it will seek assurance from Transpower that any corrective actions will be done urgently.
Genesis said it had one Rankine unit was already running on coal at Huntly Power Station today. In response to the request for more generation, Genesis has put that Rankine into "overload mode" which will enable another 10MW of generation to help get through the evening peak.
''We are also extending the planned running of our 50MW peaker unit at Huntly beyond 8.30pm this evening, when it was originally due to shut down,'' the company said.
In preparation for tomorrow, should the country require more generation than originally planned, Genesis is ramping up two more Rankine units now.
It will be 3am before either of these is able to generate due to the lead time it takes to warm them up to generating capacity. Collectively they will provide energy security through tomorrow morning's peak and throughout the day should they be needed, Genesis said.
Collectively the two Rankines will provide an additional 500MW of capacity.
