Electricity Asset Management Plan 2019-2029
182
Vector Limited://
TARGETED OUTCOMES
CUSTOMER EXPERIENCE
SAFETY
RELIABILITY
RESILIENCE
OPERATIONAL EFFICIENCY
CYBER SECURITY AND PRIVACY
OPTIONS CONSIDERED Options to address the need identified above have been assessed and are summarised in the following table.
DESCRIPTION
DISCUSSION OF OPTION
ESTIMATED COST (NPV IF APPLICABLE)
STATUS
Option 1: Business as usual – Do nothing
Failure of switchgear in Hobson ZSS will result in lengthy loss of supply to many (high profile) customers (and the associated negative impact on SAIDI and SAIFI). Failure of the switchgear also means that the security of the supply to the lower and mid CBD will be compromised and any further network contingencies will result in a complete loss of supply. The civil and structural works to make the old switch building seismically compliant and extend the 22 kV switchroom on this space constrained and operational site will be complex, costly and not without risk but has to be undertaken to ensure the integrity of the facility. The 11 kV switchgear must be replaced to ensure the continued reliability of supply to the CBD. The same holds true for the 22 kV switchgear for which partial replacement must commence to ensure continued reliability.
Rejected
Option 2: Undertake the seismic building compliance work, refurbish the 11 kV switchgear and commence with replacement of the 22 kV switchgear
$14.50M Selected
PROPOSED INVESTMENT SUMMARY ($MILLION NOMINAL)
DESCRIPTION
FY20
FY21
FY22
FY23
FY24
FY25
FY26
FY27
FY28
FY29 TOTAL
Hobson 11kV SWBD replace
2.80
3.55
3.35
9.70
Auckland Seismic Rebuild Hobson
3.80
3.80
Hobson 22kV SWBD Extension
0.50
0.50
1.00
Total CAPEX
6.60
4.05
3.85
0.00
0.00
0.00
0.00
0.00
0.00
0.00
14.50
11 KV SWITCHGEAR REPLACEMENT
NEEDS STATEMENT 11kV Primary switchgear in zone substations is among the most critical assets for lines companies. Vector’s large population of 11 kV oil-filled switchgear dates from the 1960s and 1970s and due to our rigorous maintenance regime, we have managed to maintain the reliability of this ageing 11kV fleet with very low impact to SAIFI and SAIDI. However, a failure mode is being observed in 1970s vintage New South Wales and Reyrolle switchgear in which bushings manufactured with synthetic resin bonded paper are failing increasingly. The 60s and 70s vintage oil filled switchgear designs are based on withdrawable CBs and do not provide the protection against the risk of arc flash as with newer generation switchgear where the switchgear is designed to withstand arc faults and is physically segregated to safely withstand internal arc faults and eliminate the risk of widespread damage to an entire installation. For most of our Reyrolle fleet of oil filled CBs we are able to retrofit vacuum CBs and have made good progress with this programme but a few substations still need to be completed. However, the Brush and New South Wales 11kV switchgear fleet are not able to be retrofitted and require a complete replacement.
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