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Dry Year Planning 2006

2006

We have detailed below two initiatives that helped with dry year planning in 2006.

Mangamarie Split
Verbal agreement to operate the split on the Wairarapa regional 110kV network was finalised with Powerco on Thursday 13th April 2006. The 110 kV link will remain split at Mangamarie as a consequence of the agreement. The necessary constraint changes in SPD are being developed and will be advised via a CAN to market participants. The split will increase the potential Bunnythorpe to Haywards power transfer by 30-50 MW. It will also reduce constraints on injection into Woodville from Te Apiti.

Bunnythorpe - Haywards Upgrade
The Grid Owner has work underway to increase the rating of the Bunnythorpe_Haywards 1 and 2 circuits. The rating changes are weather dependent, and it is planned that these will become operational by mid May at which time the thermal rating of the circuits will be raised from 530/647 to 807/880 amps. We expect transfer into Wellington over the Bunnythorpe_Haywards route will increase by approx 90 MW over the previous winter day-time limit of 800 MW, with all circuits in service. The re-rating will alleviate the need to rely on the existing HVDC run-back scheme overnight. 

A planned daily outage is underway on the Bunnythorpe to Haywards route until 27th April 2006. This outage will reduce south transfer into Wellington by approx 150 MW during the day. The circuit will be returned to service overnight. As this work coincides with outages that split the Wairarapa 110 kV network the split is expected to reduce the impact of the Bunnythorpe-Haywards outage on south transfer by ~30- 50 MW. The outage has been reviewed in light of dry year considerations. Transpower believes the benefits of undertaking the work exceed the short term constraints on south flows that will arise from the outage. 

Background

Following the 2001 fuel shortages Transpower has put in place several initiatives to enhance the ability of the power system to deliver high levels of southwards transfer through the North Island grid and into the South Island. The following list summarises the various issues affecting north to south transfer.

Summary of Issues

• Export south from Taranaki
• Transfer from Bunnythorpe to Haywards
• Wellington Load
• HVDC
• Reserves in the South Island
• Summer-winter rating change
• Outages

Further information on initiatives and issues for maximising north to south transfer are contained in this document:

You can also view a presentation from the industry briefing hosted by Transpower on Tuesday 11th April 2006: