Electricity Asset Management Plan 2019-2029
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Vector Limited://
Figure 4-28 Asset Health at Year 10 - Distribution Ground Mounted Switchgear
Strategy Our strategy for distribution switchgear relies on a deterioration in condition being identified by routine maintenance inspections and replacement undertaken as required by the risk under a corrective maintenance programme. Our concern is that the population has a similar age profile with large numbers approaching the end of expected service life simultaneously and a sudden increase in deterioration / asset failures becomes a higher probability and may encompass a greater number of assets that can be attended to under the budgeted corrective maintenance programme. The replacement strategy is to undertake a scheduled programme over a number of years, replacing oil-filled ring main units, with priority based on asset health, criticality and risk, including the lack of arc flash protection. Our CBARM model for this asset class is fully developed and is informing our replacement programme. Details of the replacement programme can be found in Section 5. We have also commenced with a programme of works to enhance our HV feeder automation by adding more remote controlled switches at cross feeder ties, mid-feeder segregation and cross zone ties. Vector is targeting critical feeders first and areas where reliability will be enhanced the most (high SAIDI feeders – high criticality feeders) and add telemetry devices to the HV network at critical points to provide network visibility and links for Vector’s Energy IoT. The additional network switches will also enhance the resilience of our HV distribution network in the sense that power will be able to be restored quicker. Whether in infrastructure systems, industrial and commercial areas or in suburban areas, transformers play a key role in the reliable distribution of energy to customers. For the future energy network distribution transformers will become even more pertinent as one of the major components for the flow of energy from distributed energy resources to customers. Our transformers are all oil filled and where we have to comply with environmental requirements due to oil volume, a transformer will be installed in a bund. For a very small number of transformers the windings are contained in a tank of synthetic organic ester and these transformers are used in situations where fire safety or protection of the environment (where other containment measures are not practical) are primary considerations, e.g. close to waterways. All transformers are fitted with manual tap changers. Population and Age Our ground mounted distribution transformer fleet ranges from small compact stand-alone transformers, transformers integrated as part of package type substations to ground mounted transformers as large as 1500kVA for high-rise buildings and large commercial or industrial customers. In the Northern network, the distribution voltage is 11 kV and in the Auckland area there are both 11 kV and 22 kV with 22 kV utilised in high density areas such as the CBD and Highbrook industrial estate. The Northern area has a large population of ground mounted transformers up to 250 kVA. The Auckland 4.6.2 DISTRIBUTION GROUND MOUNTED TRANSFORMERS Overview
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