Electricity Asset Management Plan 2019-2029
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Vector Limited://
PROPOSED INVESTMENT SUMMARY ($MILLION NOMINAL)
AMP19
FY20
FY21
FY22
FY23
FY24
FY25
FY26
FY27
FY28
FY29 TOTAL
Belmont 33kV SWBD ODID
1.62
1.62
Browns Bay 33kV SWBD ODID
0.65
0.65
New Lynn 33kV SWBD ODID
0.20
2.30
2.50
Sabulite 33kV SWBD ODID
0.15
1.23
1.38
Henderson Valley 33kV SWBD ODID
0.20
1.73
1.93
James St 33kV SWBD ODID
0.20
2.00
2.20
Hobsonville 33kV SWBD ODID
0.20
2.00
2.20
Sunset Rd 33kV SWBD ODID
0.20
1.80
2.00
Waikaukau 33kV SWBD ODID
2.00
2.00
Total CAPEX
2.47
2.45
1.43
1.73
0.20
2.20
2.00
0.20
1.80
2.00
16.48
HOBSON ZONE SUBSTATION UPGRADES AND REPLACEMENTS
NEEDS STATEMENT Hobson zone substation is one of three bulk supply (zone) substations in Auckland’s CBD (the other two bulk supply zone substations in the CBD are Liverpool and Quay St). Hobson ZSS is supplied from the NAaN 220 kV cable via a 250 MVA 220 kV/110 kV transformer. The voltage is stepped down to both 11 kV and 22 kV to supply the lower to mid CBD and the 22 and 11 kV nodes provide backup supply to the 11 and 22 kV networks from Liverpool and Quay zone substations. Because of the increasing load density, a long-term programme exists in which the distribution network in the CBD is being changed from an 11 kV network to a 22 kV network but this programme of works is expected to take at least another three decades to complete. This means that the 11 kV switchboard at Hobson ZSS will be required for the same amount of time. The 11 kV switchboard at Hobson consists of two sections: A Reyrolle switchboard that was installed in 1984 and a Brush switchboard that dates from 1969. This critical switchgear ZSS is approaching the end of its asset life and the risk profile offered by this plant is increasing. Failure of ageing 11kV oil-filled CBs can result in catastrophic explosions with accompanying flaming oil and shrapnel. International records exist of catastrophic and deflagration failures of similar oil- filled Brush 11kV switchgear and this holds risk of injury as well as risk of collateral damage. A number of oil-filled switchgear failures that resulted in deflagrations and extensive outages have occurred in Vector’s network in recent times most notably at Parnell zone substation (ZSS), Browns Bay ZSS and Spur Rd ZSS. Thus far catastrophic failures have negatively impacted SAIDI and SAIFI but not resulted in injury or worse. Older generation oil-filled 11kV switchgear does not provide the level of protection to personnel against the risk of arc-flash that is provided by modern gas-filled switchgear. An arc-flash has the potential to do serious harm and Vector is obliged under the Health and Safety in Employment Act and the Electricity Act to consider this risk. Both the replacement switchgear and the retrofit switchgear will provide arc-flash protection to improve the safety of personnel. The asset life of the existing 1984 vintage 11kV oil-filled Reyrolle switchgear can be extended by the installation (retrofitting) of vacuum CB trucks and the replacement of its electro-mechanical protection systems with modern numerical protection relays. A retrofit option does not exist for the 1969 vintage Brush switchgear and it will have to be replaced in its totality. Furthermore, the 22 kV Yorkshire switchgear in Hobson ZSS has been in service since 1975 and the operational performance and maintenance requirements did not quite meet expectations and a start will be made to replace this switchgear by installing a number of replacement 22 kV CBs. A staged replacement will take place with the complete suite replaced over the longer term. Before refurbishment of the 11 kV switchgear or replacement of the 22 kV switchgear can take place, a seismic upgrade is required for the switchgear building and cable basements to bring it up to seismic standard for importance level 3 buildings as required in the NZ Seismic standard and as required by Auckland Council. The 22 kV switchroom must also be extended to house the replacement 22kV switches and this civil work is also enabled by the seismic compliance works.
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