Electricity Asset Management Plan 2019-2029
199
Vector Limited://
OPTIONS CONSIDERED
DESCRIPTION
DISCUSSION OF OPTION
ESTIMATED COST (NPV IF APPLICABLE)
STATUS
Option 1: Do nothing
A Do-nothing approach means that the LV network will not be suited to the ever increasing reliance of customers on the electricity network. As society becomes more dependent on technology and the techno-dexterous population ages, the expectation is that the tolerance for loss of power will be reduced Undertake the replacement of certain components and portions of the LV network as required that will include ageing PILC LV cables and ageing and poor performing sections of the OH network
Rejected
Option 2: LV Network Replacement
$12.00M Selected
PROPOSED INVESTMENT SUMMARY ($MILLION NOMINAL)
DESCRIPTION
FY20
FY21
FY22
FY23
FY24
FY25
FY26
FY27
FY28
FY29 TOTAL
Auckland LV network replacement
1.50
1.50
1.50
1.50
6.00
Northern LV network replacement
1.50
1.50
1.50
1.50
6.00
Total CAPEX
0.00
0.00
0.00
0.00
0.00
0.00
3.00
3.00
3.00
3.00
12.00
5.2.4 DISTRIBUTION SUBSTATIONS AND VOLTAGE REGULATORS The following sections set out the project proposals for distribution substations and voltage regulators.
GROUND MOUNT DISTRIBUTION SWITCHGEAR (OIL) RENEWAL
NEEDS STATEMENT Vector’s population of ground mounted oil filled distribution switchgear is approximately 7,331 tanks (discrete oil tanks). These tanks make up 4,100 distribution substation sites of which 80% are in the Auckland network. As of 2019, approximately 506 units are already older than 50 years. The oldest unit dates from 1959 and a number of units date from the early 1960s. By 2029 another 1743 units will be 50 years old. Additionally, there are presently 1,230 SD Series 1 units in service on the network which have a known risk of failure inherent with their original design (see Section 4 for more details). In the past, our strategy relied on asset condition being identified by routine maintenance inspections and replacement undertaken as required based on the identification of risks under the corrective maintenance programme. Approximately 1% of the ground mount distribution oil switchgear population is replaced annually due to customer initiated growth or projects. Our concern was that with a population of similar age profiles all approaching the end of expected service life together that this will result in a bathtub curve scenario where there is a risk of a sudden increase in deterioration of a large population group that is likely to encompass a greater number of assets that can be attended to under the budgeted corrective maintenance programme, resulting in increased asset failures. In general, it is highly questionable that we can continue to stretch the service life of our ageing distribution switches beyond 60 years through the existing maintenance programme, due to the risk of material fatigue leading to equipment failure - especially as there are parts in the switches which cannot be maintained or replaced individually. The exception to this is the population of 1,442 J4, GF3 and T4GF3 switch units dating from 1973 onwards where we are investigating a refurbishment option in conjunction with an UK based organisation that offers after-market support options for these switch units. We are aware that a similar refurbishment approach is being utilised by a number of the distribution network operators in the UK in order to extend the life of these units by up to 20 years. Of the 2,249 units expected to exceed 50 years old within this AMP period, 956 units may be able to be refurbished rather than replaced. To embark on a long-term strategic programme to modernise our ground mount distribution oil switchgear population we fully developed a CBARM model for this asset class in the first instance to inform our replacement programme. Our planned programme will see the replacement or refurbishment of ~ 1,500 RMUs with poor asset health, high probability of failure and high criticality over the 10 year AMP period. The CBARM model has also been calibrated to factor in the poor design SD series 1 units which suffer from low phase clearances within the small tank, and therefore pose additional risk in terms of failure especially during operation (on some models we have to use ‘lanyard’ (remote) switching to ensure the safety of operating personnel).
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