KEY POINTS:
The group looking at whether enough power will be available for peak winter demand has concluded there is unlikely to be any impact on supply to consumers.
The only impact would be if there was a sudden unexpected failure of a large generating unit when the system was in the so-called "emergency" state where supply balances demand.
The finding is included in an updated report by the National Winter Group (NWG) of industry participants on the power system's ability to meet peak winter demand.
Complicating the issue is the status of the link which carries electricity between the South and North Islands.
Last September, Transpower stood down the so-called Pole 1 of the link, initially reducing the capacity of the link from 1000 megawatts (MW) to 500MW. It has since increased the south to north transfer capacity of the other part of the link, Pole 2, to 700MW and is working towards returning half of Pole 1 to service, in a limited mode of operation.
Transpower chief executive Patrick Strange said the transmission grid operator was confident it would be able to do that.
Since the NWG's initial report in December, confirmation has also been received that the New Plymouth power station will not return to service, after the discovery of asbestos.
In its report yesterday, the NWG said that if Pole 1 was not available, but all other generation was, there was a medium confidence the power system would be in its normal secure state at peak winter demand time.
If Pole 1 was available there was a high confidence the power system would be in its normal secure state during peak winter demand periods. If a large generating unit was unavailable and all other generation plus Pole 1 was available there was a medium level of confidence the power system would be able to be operated in the secure state.
But if Pole 1 was not available in that situation it was expected the power system would operate in the emergency secure state during some winter evening peaks from June to mid-August. In the emergency secure state the automatic disconnection of a significant number of consumers is possible at peak times in the event of the loss of a large generator or the inter-island link.
Dr Strange said the NWG had recommended a number of positive demand side management initiatives that could be put in place before winter to help at peak times.
Transpower believed that would be good practice and would ensure progress was made on the initiatives.
The NWG said its report should not be read as expressing a view on overall power system adequacy for winter 2008, particularly the "dry year" risk.
Monitoring that risk is a separate process from that carried out by the NWG and is run by the Electricity Commission. Dr Strange said that whether or not Pole 1 was in service had no bearing on the management of drought issues, which had resulted in lower-than-average lake levels.
"The industry has worked very well together to ensure that the recent North Island generation issues were managed appropriately, and we will now work together in addressing the separate issue of low lake levels going into winter," he said.
- NZPA
