Electricity Asset Management Plan 2019-2029
105
Vector Limited://
4.4 DISTRIBUTION FEEDERS HV Vector’s HV distribution network is for the larger part operated at 11 kV. In the Northern supply area, the HV distribution network is predominantly overhead but in new subdivisions HV networks are installed underground. The underground HV network is extensively interconnected via distribution substations. In the Auckland supply area, the HV distribution network is predominantly 11 kV underground but there are pockets of overhead supply most notably the lengthy rural supply to Maraetai and further south to Kawakawa Bay. In the Auckland CBD and in the Highbrook industrial estate, 22 kV networks are utilised for distribution – 22 kV distribution is for the most part underground. Vector has 3776 km route length of 11 kV overhead (OH) distribution feeders. The overhead conductor types and sizes vary across the overhead network and are predominantly copper (Cu), all aluminium conductors (AAC) or aluminium conductor steel reinforced (ACSR) conductors. Aluminium alloy conductors (AAAC) are being utilised for new line construction. Overhead air break switches and gas-filled overhead switches that can be remote controlled via SCADA exist in strategic locations in the overhead distribution networks to allow automated circuit breaking and controlled remote switching by the EOC to quickly and effectively control the network to limit SAIDI and SAIFI during switching after a fault to restore supply or for planned works. Population and Age A breakdown of the 11 kV OH distribution network is given in the table below but it must be noted that due to historical legacy issues, there are deficiencies in the information of the ages of conductors (and poles) for certain areas in the Auckland region. Copper conductors installed in the 1940s through to 1960s are experiencing failures. The table below summarises the population of 11 kV while the graph provides an age profile of 11 kV conductors. 4.4.1 DISTRIBUTION FEEDERS HV OVERHEAD Overview
DESCRIPTION
AUCKLAND
NORTHERN
No of 11 kV OH distribution feeders
286
281
Circuit length of 11 kV OH distribution feeders – all conductor types
890 km
2886 km
Circuit length of 11 kV OH distribution feeders Aluminium conductor
248 km
2467 km
Circuit length of 11 kV OH distribution feeders Copper 12 conductor
603 km
405 km
Table 4-11 Key statistics for HV OH conductors
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12 The age data for Copper conductors in especially the Auckland network has historical errors in it and data will remain unavailable. The quantities for conductors in especially the Auckland region contains a proportion of estimation
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