Electricity Asset Management Plan 2019-2029
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Figure 4-12 Age Profile for Primary Switchgear
Condition and Health We have undertaken considerable investment on Liverpool 110 kV switchgear in 2014 to improve the health of this highly strategic switchgear in the Auckland CBD. The 110 kV switchgear in Hobson zone substation is only five years old. A number of our 33 kV outdoor oil filled CBs date from the early 1960s and there has been catastrophic failures in this fleet. A number of 11 kV switchgear suites date from the 1960s as well. In the last two years, we have observed failures of 1980s installed 11 kV vacuum breakers – one of which resulted in the failure of the 11 kV switchgear in Mt Wellington zone substation in January 2018. Strategy Our 110 kV switchgear is regularly maintained and the Hobson 110 kV switchgear has on-line gas pressure monitoring to our control centre. The Liverpool 110 kV switchgear will be fitted with on-line gas monitoring in the next financial year. 33 kV outdoor oil filled CBs are replaced based on asset health and criticality and the same goes for our 11 kV switchgear. Our 22 kV SF6 switchgear in Quay St zone substation in the CBD is one of our oldest gas insulated switchgear suites and will undergo a mid-life CB mechanism refurbishment in 2019 and circuit breaker fail protection will be installed. We have procured a vacuum interrupter test set and have setup a programme to test all older vacuum current interrupters in our 11 kV fleet. Our CBARM model, to further assist the evaluation of our switchgear fleet, is presently being developed and will be completed in FY19. The future electricity network and load scenarios are not expected to impact our programme for replacement because age, condition and criticality as well as health and safety concerns will be the primary factors that will impact on and inform our selection and planning of the replacement programme. However, the future electricity network and associated load forecast will be evaluated with regard to how many CBs will be replaced, i.e. a low growth forecast could result in fewer CBs to be replaced and vice-versa. The 2.3 MWh battery storage system at Glen Innes zone substation has now been in service for nearly three years to supply peak demand. Our second and third battery storage systems were recently commissioned at Warkworth South and Snells beach zone substations (2.0 MW/4.8 MWh and 2.75MW/6.7MWh respectively). A 1 MW/1.7 MWh storage system is being planned in the remote Kawakawa Bay rural area as part of a microgrid that will provide respite to customers during outages on the long 11 kV rural feeder to this area. Commissioning of the Kawakawa BESS is anticipated in FY20. A 1 MW/2 MWh BESS is under construction at the Hobsonville Point zone substation and 4.3.3 BATTERY ENERGY STORAGE SYSTEMS (BESS) AND MICROGRIDS Overview
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