Electricity Asset Management Plan 2019-2029
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that will lead to unintentional shorts in the insulation of which a high number are not repairable. Depending on the condition of transformers, mid-life refurbishment is an option to extend the lives of transformers.
We take care not to subject our transformers to excessive loading and they undergo regular testing in accordance with our maintenance regime. The availability of spare parts especially for tap changers, will impact our decision on whether to refurbish a transformer or to replace a transformer. We are finding replacement parts for certain older generation tap changers almost impossible to source. Notwithstanding our maintenance and testing regime, the asset health of a number of older power transformers has now reached a stage where mid-life refurbishment is not an economical option. Development of our CBARM model for power transformers is in progress at the time of writing. Notwithstanding, our strategy is to progressively replace the population of power transformers that have the worst asset health and are the most likely to suffer major failures. The investment summary below is our current view to replace power transformers but this will continue to be informed by on-going condition monitoring that might change priorities.
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 to retain ageing power transformers in service
The replacement of a large power transformer is a challenging and time consuming task that can take months rather than weeks at which time the supply will be on ‘N’ security. Any further failures could mean that load cannot be serviced with a commensurate risk of high SAIDI and reputational damage. This option is not recommended Our ‘Symphony’ modelling scenario shows that there will be natural load growth to which EV charging will contribute. Modelling also shows that there will be a decrease in demand due to efficiencies and small scale batteries and solar distributed generation. However ,modelling shows that new technology options will not reduce peak demand in the AMP period to such an extent that it will negate the need for power transformer replacement. A BESS system will assist during peak demand but will not improve or provide security of supply for failure of a power transformer in this AMP period. This option is not recommended To ensure continued long-term reliability at zone substations a programme of works should be undertaken to replace power transformers with the worst asset health and highest criticality. This will ensure that security of supply standards and service levels to customers will continue to be met and will also reduce the risk of injury due to for example a failed tap changer
Rejected
Option 2: Use new network technology options such as a BESS system to offset the requirement to replace zone substation power transformers
Rejected
Option 3: Undertake a staged and scheduled programme of works to replace zone substation power transformers
$34.12M Selected
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