Dry Winter Planning


Since February, hydro storage has been declining due to low inflows in the South Island. We are currently experiencing a dry winter.

Transpower, as system operator, has specific duties to monitor, analyse and, if required, manage dry winter situations. We also oversee the administration of policies which govern how New Zealand security of supply is managed. 

Storage in the South Island crossed the 1% Hydro Risk Curves (HRCs) on 22 May 2017, followed by storage crossing the New Zealand 1% HRC on 27 May 2017.    However, recent inflow events have returned storage to above both the New Zealand and South Island 1% HRCs.Therefore, the likelihood of requiring any emergency response, such as an official conservation campaign, is low. 

As security of supply risk can change rapidly we are still monitoring the situation closely and have emergency plans ready to go should they be required. 

The page will be updated on an as required basis, and was last updated on 3 August 2017.

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General information

Over the course of the last few months we have carried out or planned for a number of activities, including, but not limited to:

  • We have analysed constraints on the power system during high HVDC transfer. Summary information and technical reports are available below.
  • Ongoing reviews of planned outages with specific focus on outages constraining HVDC south transfer, constraining hydro generation on or constraining thermal generation off. Currently, we have no plans to defer or cancel outages unless the situation deteriorates.
  • We have implemented a variable line rating for the Livingstone-Naseby 1 and Naseby-Roxburgh 1 circuits.
  • We assessed the benefit of a special protection scheme in the lower South Island, this work has been stopped as part of this work stream, it will now be assessed, prioritized and delivered as appropriate through Transpower’s Grid Operating Model.

Other Relevant Information

South Power Transfer Challenges Overview 2017 [ pdf 663.97 KB ]
North Island Constraints during high HVDC South Transfer [ pdf 725.44 KB ]
South Island Constraints during high HVDC South Transfer [ pdf 770.56 KB ]
Summary of 14.06.17 Dry Year Teleconference with industry [ pdf 114.66 KB ]
Summary of 06.07.17 Dry Year Teleconference with industry [ pdf 335.72 KB ]

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