Electricity Asset Management Plan 2019-2029
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Vector Limited://
programme will continue in the AMP period and most likely beyond until all circuits in the CBD are 22 kV – details of this programme is in Section 5. Unless a programme of intervention is undertaken in this AMP period, by 2039, the amount of 11 kV cables at end of reliable life will be triple that at the end of this AMP period, 2029. Our CBARM model for underground HV distribution cables is currently under development and will better inform us to plan our intervention programme of works. With regard to new electricity networks in suburban areas the Auckland Council Unitary Plan requires urban reticulation for new developments to be placed underground and Vector works with developers and property owners to deliver this outcome. Our development plans for future networks in land defined for suburban development and subdivisions will be based on our Symphony future networks modelling scenario.
A large body of works has already commenced to increase automation of the HV underground network to reduce SAIDI and the positive impact of the increased number of distribution substation sites with automation can already be seen.
4.5 DISTRIBUTION FEEDERS LV Overview
The LV network is predominantly overhead in the Northern region and consists of mostly bare conductors. The LV network shares HV support structures for extensive parts of the network and on many routes subtransmission circuits exist on the same support structures – Glenfield on the North Shore is a notable example where 110 kV, 33 kV, 11 kV and LV circuits exist on many of the same support structures. In new networks all LV feeders are underground cables. A mixture of above ground pillars and buried service pits are used to tap off to customer connections from our LV underground networks. For the larger part of the LV network, circuits have limited interconnections and in some cases are not designed for full backstopping if an adjacent distribution transformer should fail. A significant challenge with regard to the LV fleet is that network data is less visible and the geospatial information system (GIS) cannot always provide an up to date view of the LV network. Historically, overhead conductors have moved from copper, to AAC and ACSR, through to AAAC. Vector has a large number of different sized conductors with some bare and some PolyVinyl Chloride (PVC) covered, some greased and some not greased. We also have a sizable population of LV ABC conductors. The larger part of the LV network in the Auckland region is underground but 37% of the LV network remains an overhead network. Traditionally, this asset class has been the asset with the least focus in terms of its age and condition, while ironically in the new energy future, will be the asset that will become more important if not the most important as the uptake for EVs, solar and customers’ DERs increases. Key statistics of the LV distribution network are stated in the Tables below. 4.5.1 DISTRIBUTION FEEDERS LV OVERHEAD Population and Age
DESCRIPTION
AUCKLAND
NORTHERN
Circuit length of LV overhead distribution feeders (km)
1960
2198
No 13 of LV network poles
28681
18559
Table 4-14 Key statistics for LV Underground Cable Network
Condition and Health Because of legacy data deficiencies we do not presently have robust data with regard to the condition and health of the LV OH network apart from information that is gained through planned maintenance inspections. We are not experiencing any systemic network failure modes in our LV network apart from the impact of vegetation during storms, which impact other parts of the OH network as well. The ageing LV network is resulting in the failure of some components such as neutral conductor clamps and this has an impact on customer service levels – a strategy to address this specific topic is in the process of being developed. The increasing importance of the LV network as the
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13 It must be noted that where LV OH circuits are installed on HV poles (i.e. share HV poles), such poles are counted under HV distribution supports and are not shown in the table below.
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