Electricity Asset Management Plan 2019-2029
150
Vector Limited://
OPTIONS ASSESSMENT For major projects, i.e. above $4M (level to be confirmed), include the following in this section: Technical feasibility, economic analysis, OPEX and CAPEX costs, net present value or net present cost, service levels, risks, etc.
DESCRIPTION
DISCUSSION OF OPTION
ESTIMATED COST (NPV IF APPLICABLE)
STATUS
Forecast security shortfall arising from residential growth at Highbury
Option 1: Install a second transformer and new sub- transmission cable to Highbury substation. Highbury substation is supported by single transformer substations comprising Balmain and Northcote, and with the proposed Housing NZ redevelopment in Northcote additional capacity is required. A second transformer and subtransmission cable are proposed Option 2: Upgrade adjacent substations of Balmain or Northcote in preference to Highbury. Both Balmain and Northcote are supported by dual transformer substations of Hillcrest and Birkdale respectively, and so the security improvement is less than for upgrading Highbury. Upgrading either of Balmain or Northcote is more costly than Option 1, due to the longer subtransmission circuits needed Option 3: 11kV load transfer. Transferring load to the adjacent substations (Balmain or Northcote) immediately causes a security shortfall at the neighbouring substation. This in turn initiates a reinforcement project as per Option 2 above but with the added cost of reinforcing the connecting 11kV feeders Option 4: Non-network solutions. The forecast load increase on Highbury cannot be offset by load management or by sensible battery solutions. Even with hot-water load control there is a capacity shortfall from 2019 onwards following the loss of either the Northcote or Highbury transformers at peak times Option 1: Install a second transformer and new sub- transmission cable to Takapuna substation. Takapuna substation is a single transformer substation supplying the Takapuna CBD. It is also a critical substation providing backup to Belmont, Hauraki and Ngataringa Bay upon loss of the double-circuit Belmont subtransmission lines. Apart from the criticality of this substation for the backup security of the Devonport Peninsula, growth in Takapuna is reducing spare capacity. A second transformer supported by a second subtransmission cable from Wairau Rd GXP is proposed Option 2: Non-network solutions. Network security cannot be delivered by these solutions Option 1: Ngataringa Bay substation rebuild. Ngataringa Bay substation is a low-lying coastal substation and has been inundated in the past on a number of occasions by king tides. Forecasts indicate the frequency and severity of these events is likely to increase. The proposal is to rebuild the substation to avoid this risk Option 2: Abandon Ngataringa Bay substation and supply load from adjacent Belmont substation. This substation supplies the Naval Base, residential load in Devonport and Stanley Point and supports Belmont substation. Transferring this load onto Belmont would immediately initiate an upgrade of Belmont as this substation is already to N-1 capacity, whereas replacing Ngataringa Bay with a new substation could be used to alleviate Belmont loading
$4.45M Selected
Rejected
Rejected
Rejected
Forecast security shortfall arising from the common- mode failure risk of the Wairau-Belmont double circuit, and insufficient backstop capacity for Takapuna ZSS
$7.3M Selected
Rejected
Address the inundation risk associated with Ngataringa Bay substation
$9.5M Selected
Rejected
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