Electricity Asset Management Plan 2019-2029
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Vector Limited://
no failure occurred in our 33 kV CB bulk oil fleet but a chunk of this asset population is of the same age and nearing the end of its design life – this can be attributed to a rigorous maintenance schedule and high standard of maintenance.
Furthermore, this fleet of CBs is not technically supported by vendors but we recovered similar CBs from previous conversion projects and these have been retained to be cannibalised for spare parts. It must be noted that if a 33 kV oil- filled CB fails it is usually catastrophically and they do present a risk to maintenance personnel as well as personnel that undertake inspections in close proximity to this plant. Because of the volume of oil that these CBs contain they also present a risk to the environment. We also have a number of first generation 22 kV SF6 switchboards that are showing signs of poor health. One 22 kV switchboard in particular is the Yorkshire SF6 switchgear suite in our Hobson zone substation in the Auckland CBD. The asset health in this switch presents reasons for concern and a programme of replacement needs to be undertaken – we will start this replacement programme by extending the existing switch with a number of new panels 17 - with a gradual transfer of 22 kV CBF feeders to the extension. The replacement programme for 33 kV and 22 kV switchgear will not result in a visible and immediate impact or improvement to SAIDI but will rather reduce the risk of catastrophic failure and prevent the high levels of SAIDI that will go hand in hand with a failure of this plant, from happening in the first instance.
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 – no additional investment: Continue with current level of investment to maintain ageing 33kV bulk oil CBs.
The existing fleet of 60s and 70s vintage CBs require extensive maintenance to keep them operational and safe. At present a number of 33kV bulk oil CBs that were recovered from previous conversion projects, are available to be cannibalised for spare parts and this enables Vector to maintain its current fleet of 60s and 70s vintage bulk oil CBs. However this stock of CBs will be depleted in the not too distant future. During maintenance, personnel work in close proximity to in service 60s and 70s vintage oil CBs and they present a risk to the H&S of personnel. The risks associated with this switchgear is of high consequence and high likelihood and failure will have a high impact on SAIDI New technology options are not suitable as an alternative for the risk posed by ageing bulk oil filled CBs
Rejected
Option 2: Use new network technology options to offset the requirement to replace subtransmission circuits Option 3: Undertake a staged and scheduled programme of works to replace 33kV outdoor bulk oil CBs
Rejected
This solution will address the risk as per the bathtub curve where outdoor bulk oil CBs of the same age is approaching the end of their design life. This option removes the risks associated with the ‘Do Nothing’ option
$16.47M Selected
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17 The works at Hobson ZSS are described in a separate Needs Statement
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