Electricity Asset Management Plan 2019-2029
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However, we are in the process of evaluating new load control systems. Some of these (a digital radio-based solution) have recently completed a successful proof-of-concept trial. Once we have settled on a preferred load-management system, it will be rolled out more widely as a replacement for our existing load-control systems during the period of the AMP. The strategy for planned maintenance to keep our existing ripple plant systems working well includes procuring some key spare components to hold in stock for quick deployment, in case of plant failure when complete plant replacement isn’t planned. We will also regularly tune these ripple plants, so they perform at optimum levels to ensure maximum reach of the ripple signal and improve propagation.
We will continue to control that part of Auckland City Council’s streetlight population to that hasn’t been transferred to their own digital remote-control network as yet.
4.1.6 OUR CBARM, REFURBISHMENT AND REPLACEMENT STRATEGY Ageing assets remain a challenge, and replacement is sometimes delayed due to uncertainty around cost recovery and replacement choices – especially in light of the ‘new energy future’ that sees growth at the grid edge increasing. Asset refurbishment and replacement also needs to be considered in the light of a future where the low voltage (LV) network continues to become more important. Our Symphony scenario foresees resilience being shared (see our reliability and resilience strategy above) so we have to be careful not to burden future generations with costly undertakings that have a long-term, regulated cost recovery period. This means full documentation and data on the operational history of our installed asset base will become even more important to understanding and managing them. This will allow us to predict possible issues early and do preventative maintenance or replace the asset. To do this, we are implementing the CBARM (Condition Based Asset Risk Management) modelling as part of our proactive replacement and refurbishment programme. CBARM first details the age profile of an asset population, then assesses the expected life and condition of individual assets. Resulting asset condition health scores allow us to identify assets that are forecast to exhibit higher likelihood of failure during our 10-year AMP period and beyond. The use of asset condition information and its health score underpins our 10-year forecasted expenditure, and is crucial in moving beyond the traditional time based asset replacement approach. The CBARM model also contains information about an asset’s criticality, that describes the potential consequences when an asset fails. This is combined with an asset’s likelihood of failure to derive asset risk. Expenditure is then prioritised during the scoping stage to identify areas of work based on risk at an individual asset level. This ensures that assets at the highest risk are prioritised appropriately. These models will continue to evolve as we improve our understanding of the risks and better network condition data is collected as a result of the new maintenance standards and associated system enhancements. In dealing with distribution assets, where we have large populations of low-cost assets and components, the optimal investment options (to repair, replace or refurbish) are relatively limited and are readily evaluated. For our more critical distribution and sub-transmission assets, such as power transformers and primary switchgear, where replacement costs are high, the optimal investment options need more complex evaluation, plus business case justification. • The impact and effect of the Symphony future-load scenario on the network and its assets • The asset’s risk and performance history • Evaluation of alternative network solutions as a permanent answer to the replace or refurbish, or defer, issue • The maintenance costs over the remaining life of the asset, and whether these will exceed those of replacing it • If the asset is no longer unsupported technically – software updates aren’t practical, and/or spares aren’t available • If the asset has become obsolete; component fabrication is expensive; the asset is likely the last of its kind and continuing with its operation is inefficient • If low-cost retrofit replacements are available with enhanced ratings and safety features Asset refurbishment is generally restricted to subtransmission transformers and a certain size of distribution transformer. This is an economic way of extending life. However, we are extending the life of some types of 11 kV switchgear by replacing 1960s’ vintage oil-filled circuit breakers (CBs) with modern vacuum CBs as this is more economic. Factors that may be considered include:
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