Electricity Asset Management Plan 2019-2029
148
Vector Limited://
A second transformer is planned for Coatesville substation (Coatesville - second 33/11kV transformer), again to address the extra load caused by urbanisation of rural areas towards the southern end of the Dairy Flats Highway (northern end captured under Silverdale).
An 11kV feeder project is proposed linking two 11kV feeders that supply Muriwai Beach area, to improve the resilience of the network in this area.
TARGETED OUTCOMES
CUSTOMER EXPERIENCE
SAFETY
RELIABILITY
RESILIENCE
OPERATIONAL EFFICIENCY
CYBER SECURITY AND PRIVACY
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 Waimauku
Option 1: Upgrade the transformers at Waimauku. Greenfields residential growth is extending from Hobsonville along SH16. The capacity in the existing substation at Waimauku will need to be increased to maintain security. One transformer is being replaced due to end-of life, the other due to insufficient capacity Option 3: DSM or network batteries: The load is increasing at an average rate of 250kVA/annum. The existing transformers are rated at 7.5MVA and 10MVA respectively, supplying a winter peak load of 11.1MVA. The current shortfall in N-1 security is provided by 11kV feeders connected to adjacent substations. As the load increases through new local developments the predominantly rural feeders run out of capacity to provide the necessary level of security. Hot water load control will provide 3 years of deferral. Installing a network battery will allow peak shaving but the most economical approach is to install larger transformers (Option 1) Option 4: Cable ducts – SH16. NZTA are upgrading SH16 as part of their safety improvements programme. We will install cable ducts along SH16 from Waimauku to Huapai in conjunction with these works to enable a future 33kV cable connection into the Riverhead subtransmission circuits and reinforce 11kV connection to Huapai, Kumeu and Riverhead. The 33kV cable will double the subtransmission capacity to Waimauku and improve the resilience of the substation to subtransmission faults. The ducts will be installed leveraging off existing roadworks to minimise disruption to the public Option 5: Defer the ducts along SH16 until the cables are required. This approach increases the risk that the cables will not be in service when needed, compromising network security. In addition to the disruption caused to the public by a separate major state highway civil project, the additional costs of not sharing the civil works with the NZTA project are prohibitive Feeder upgrade at Muriwai. This project is to improve the resilience to customers on the end of the Muriwai beach feeder by linking two radial spur lines.
$1.8M Selected
$0.6M Load control
Rejected
$4.2M Selected
Rejected
SAIDI Improvement Initiative
$0.8M Selected
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