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Lower South Island Reliability
Transmission Investment Proposal
Submission from
Contact Energy Limited
Lower South Island Reliability Transmission Investment Proposal - 30 June 2010
Introduction
Contact welcomes the opportunity to provide feedback on Transpower’s investment proposal.
The information in this submission is not confidential.
For any questions related to this submission, please contact:
James Collinson-Smith
Manager – Market Services
Contact Energy Limited
L 1 Harbour City Tower
29 Brandon Street
PO Box 10742
Wellington
Email: [email protected]
Phone: (04) 462 1249
Fax: (04) 499 4003
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Lower South Island Reliability Transmission Investment Proposal - 30 June 2010
Summary
Contact Energy Limited (“Contact”) supports Transpower’s aim to ensure appropriate investment
is made in the national grid to meet the needs of electricity consumers and generators.
Contact fully supports this investment proposal because it will add essential core-grid capacity
between Roxburgh and Invercargill, and it will also provide much needed security of supply to
Southland consumers supplied from the 110kV system. Any further increases in constraints on
the 110kV system are likely to be detrimental to retail in the Otago-Southland area.
These grid upgrades are overdue, as capacity and voltage problems arise whenever a 110kV or
220kV circuit is removed. The Roxburgh interconnecting transformer (T10) overloads under
certain load flow scenarios (i.e. during low ROX 110kV generation), T10 may overload with an
outage of the Halfway Bush interconnecting transformer (or either of the INV_ROX 220kV circuits,
or either of the ROX_TMH 220kV circuits). Contact has to manage this operationally through
Roxburgh 110kV generation and therefore wants the Roxburgh T10 interconnecting transformer
to be upgraded as soon as possible.
Contact cannot guarantee continued voltage support to the 110kV system, as without some
certainty of the Roxburgh T10 upgrade we may be incentivised to transfer the Roxburgh G6
generating unit to the ROX 220kV bus. Note that we have not refurbished Roxburgh G8 and
therefore it should not be assumed that this would be available for voltage support.
The lower South Island (“LSI”) region is unique in that it is dominated by the NZAS Smelter load,
important dairying load, and has the potential for a number of large generation developments
therefore it is important that security is maintained under a range of scenarios. Each of the
generation developments could impact significantly on the timing of grid development
requirements in the region.
In terms of incentives for new generation developments, Contact notes that Transpower’s
generation assumptions do not consider the potential changes in the transmission pricing
methodology (“TPM”) with respect to HVDC charges. This reduces the incentives to invest on the
core grid in the South Island. If the TPM were to change such that HVDC charges to South Island
generators were removed then it would raise the merits of potential South Island developments
relative to other options. Should Trustpower’s Mahinerangi windfarm be built to its consented
200MW all Roxburgh 110kV, generation may be transferred to the Roxburgh 220kV bus.
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