Electricity Asset Management Plan 2019-2029
201
Vector Limited://
PROPOSED INVESTMENT SUMMARY ($MILLION NOMINAL)
DESCRIPTION
FY20
FY21
FY22
FY23
FY24
FY25
FY26
FY27
FY28
FY29 TOTAL
Auckland RMU replacement
6.40
7.00
8.50
9.50
9.50
9.50
10.00
10.00
10.00
10.00
90.40
Northern RMU replacement
1.60
1.60
2.00
2.00
2.50
2.50
3.00
3.00
3.00
3.00
24.20
Total CAPEX
8.00
8.60
10.50
11.50
12.00
12.00
13.00
13.00
13.00
13.00
114.60
DISTRIBUTION TRANSFORMERS REPLACEMENT
NEEDS STATEMENT There are approximately 7,600 pole mounted distribution transformers operating in Vector’s network. Almost three quarters of this population is in the Northern network that is a predominantly OH network. With respect to the age of the equipment, almost two thirds of the population are installed in the 1990s or thereafter. Some of the oldest units have been in service since the 1950s. Given the design life expectancy of a distribution transformer typically ranges from 30 to 40 years, the transformers installed in 1980s and prior – approximately 2,700 units – will reach the end of design life by 2029. There are approximately 14,200 ground mounted distribution transformers operating in Vector’s network. The population is evenly split between the Auckland and Northern networks. With respect to the age of the equipment, half of the population were installed in the 1990s or thereafter. The oldest units have been in service since the 1950s. Ground mounted distribution transformers have a similar life expectancy as pole mounted units namely in the range of 30 to 40 years. This means that ground mount transformers installed in the 1980s and prior – approximately 6,400 units – will reach end of design life by 2029. Vector’s current maintenance strategy for this equipment class relies on regular visual inspections to identify any noticeable deterioration in exterior of a transformer, and then undertaking replacements as required. Due to practical constraints, no testing is performed as part of the maintenance regime on an in-situ transformer to assess the electrical performance and properties of its insulation. In addition to the condition-based replacements, approximately 1.6% of the population is replaced annually for other purposes, such as new customer connections, network reinforcement etc. Our concern with the existing population is that there is a large number of transformers of similar ages approaching expected end of service life in the coming decade, and if we continue to allow this situation to develop unabated, it could result in a scenario where the incidence of simultaneous transformer failures in the network rises suddenly and in considerable quantities that will create a large burden on all resources, such as field staff, corrective budgets, and the ability of equipment manufacturers to respond effectively to the failures. Such a scenario will have a commensurate negative impact on reliability indices and on service level targets. To address this we need to adopt a different asset management approach to manage Vector’s distribution transformer population rather than continuing to rely on the traditional time based maintenance approach. Hence, we have developed a CBARM model as a tool to help us identify distribution transformers that need to be replaced based on asset health, probability of failure and criticality factors. The outputs of our CBARM model are going to be used in the development of a comprehensive maintenance and replacement programme for distribution transformer for the next 10-year AMP period. This programme of works will require the replacement of 1,556 pole mounted transformers and the replacement of 1,680 ground mounted transformers over the AMP period. By undertaking this long-term strategic plan for pole mount and ground mounted transformers, it not only ensures continuous reliability of this asset class but also reduces the risk of unexpected transformer failure to a manageable level.
The following graph shows the expected asset health profile at the end of the 10-year AMP period if the proposed replacement programme is undertaken for pole mounted distribution transformers.
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