Electricity Asset Management Plan 2019-2029
146
Vector Limited://
DESCRIPTION
DISCUSSION OF OPTION
ESTIMATED COST (NPV IF APPLICABLE)
STATUS
Forecast security shortfall arising from residential growth at Millwater and Wainui
Option 1: Upgrade the 11kV switchboard at Orewa substation. The incomer rating of the switchboard is 800A (15.2MVA) which is below the capacity of the subtransmission circuits, transformers, and current peak load. Replacing the switchboard with one of higher rating will release available capacity Option 2: Construct Millwater Zone substation. To support the forecast growth in Wainui and Millwater, a new zone substation is proposed Option 3: Defer the expansion of Orewa substation by constructing Millwater zone substation (or vice versa). Orewa substation is a long way from the face of the residential development, requiring the installation of additional long 11kV feeder cables to deliver the capacity to new growth. This is costly and inefficient. It is preferable to have the substation located at the future load centre i.e. Millwater substation. Installing a new switchboard at Orewa and a new substation at Millwater allows the redistribution of load on Orewa substation supplying new growth to the north of Orewa, and has a lower NPV cost Option 4: Hibiscus Coast 11kV reinforcement. Feeder and backstop capacity will be exceeded between Orewa and Red Beach substations. A new cable will resolve the constraint. Option 5: Delay primary asset investment through DSM or new technology solutions. Hot water load control is estimated to deliver 1.4MW or approximately two years growth at present rates. The NPV calculation based on the installation of HLC followed two years later by Millwater substation (or Orewa) favours Millwater as the best option Option 1: Kaukapakapa zone substation: Construct Kaukapakapa substation and segment feeders. This will reduce the number of customers per feeder thus improving SAIDI, reducing the length of the feeders and enabling closer protection. Kaukapakapa substation will also support Helensville substation Option 2: Helensville zone substation: The existing transformers are scheduled for replacement. When replaced they will be upgraded from the current 2 x 12.5MVA to 2 x 15MVA units Option 3: Install additional 11kV feeders to provide backup support. The construction of Kaukapakapa substation under Option 1 will initiate 11kV reinforcement to ensure maximum resilience benefit is gained. However, without the substation, the equivalent resilience benefit can only be achieved by substantially increasing the investment in extending the 11kV. This option is unnecessarily costly and ultimately ends up with asset stranding Option 4: South Head micro-grid: The 11kV feeder from Helensville to South Head is over 50km long and lacks a back-up supply. It is one of the worst performing feeders caused in part by its length, proximity to westerly weather events and remoteness. Installation of a micro-grid towards the end of the feeder will allow supply to be maintained to some of the more remote customers when an outage occurs
$3.10M Selected
$8.28M Selected
Rejected
$2.0M Selected
$0.6M Rejected
Improve the resilience of the network in the Helensville area
$7.5M Selected
$1.7M Selected
Partially selected
(some 11kV reinforcement included in Option 1)
Under analysis
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