Transpower issues another emergency notice for grid

There are warnings of potential power cuts soon after another Grid Emergency Notice from Transpower.

The notice, sent at 4:23pm, covers between 5pm and 7:30pm on Tuesday night.

Transpower's warning there's the risk of "insufficient energy offers in the North Island to meet demand plus instantaneous reserve requirements".

"Transpower as system operator advises there are insufficient generation and reserve offers and transmission capacity to meet demand and provide for N-1 security for a contingent event," it states.

"The level of instantaneous reserves being scheduled may or will be reduced".

In a subsequent release it blamed the situation on a conductor wire that fell from a tower in North Canterbury.

Transpower added it's 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)," it explained.

"If this does not achieve the reduction we require, we will issue a further notice setting a further target for demand reduction."

Counties Energy has sent an urgent message to its customers on Facebook, warning of "potential power loss soon".

"Please prepare for potential loss of power. We will keep you updated as soon as we know more," it wrote.

"Please share with those you know and keep an eye out on the vulnerable. Medically dependent please put your power loss plans into place."

It comes after tens of thousands of properties were plunged into darkness on Monday last week after Transpower pulled the plug on homes.

It explained insufficient generation was available to meet demand and so it asked distribution companies to reduce load across the country.

Transpower operations general manager Stephen Jay told The AM Show afterwards that Transpower looks and asks for "offers" of generation from various sources around the country and then matches that in terms of what the demand will be.

 Ensuring the electricity is transmitted requires management in real time, Jay said, and relies on a mix of generation as well as ensuring "all of that generation works when requested".

"It relies on the generators putting enough offers into the system to allow us as the operator of the system to basically request that that generation comes on."