Electricity Asset Management Plan 2019-2029
197
Vector Limited://
Note an additional corresponding increase in maintenance replacement expenditure is associated with this option (refer need statement for Network Maintenance)
PROPOSED INVESTMENT SUMMARY ($MILLION NOMINAL)
DESCRIPTION
FY20
FY21
FY22
FY23
FY24
FY25
FY26
FY27
FY28
FY29 TOTAL
Auckland right of way hardware replacement Northern right of way hardware replacement
3.80
2.50
2.50
2.50
2.50
2.30
1.00
1.00
1.00
1.00
20.10
6.20
2.50
2.50
2.50
2.50
2.30
1.00
1.00
1.00
1.00
22.50
Total CAPEX
10.00
5.00
5.00
5.00
5.00
4.60
2.00
2.00
2.00
2.00
42.60
11 KV UNDERGROUND CABLE REPLACEMENT
NEEDS STATEMENT Vector’s 11 kV distribution underground cable network for the combined Auckland and Northern networks is 3,542 km in route length of which about 285 km will be past end of reliable life at the end of this AMP period – see Section 4 for details of the existing 11 kV underground distribution cable population. There is a further 160 km of cables for which there is no age data (a legacy data issue for older asset populations). Underground 11 kV cables have a long asset life but our 11 kV cable population is ageing and over the last two years Vector has observed an increase in the number of 11 kV cable failures. Another failure mode that is on the increase is deteriorating tinning on tinned aluminium lugs on outdoor 11 kV cable terminations on 11 kV cable risers to OH lines. We could continue to repair faulted cable but for certain sections of cable the fault history, frequency of faults together with diagnostic testing means that replacement should be undertaken. We have commenced with a programme to test cables with suspected poor asset health and have found a number of 11 kV cables have very low insulation levels which is an indication that this portion of the fleet is approaching end of life. Unless a programme of intervention is undertaken starting in this AMP period, our prediction of asset health is that by 2039, the amount of cables at end of reliable life will be triple the amount in 2029 – see the graph below. An increasing cable failure trend will impact negatively on SAIFI, SAIDI, and on customer service levels.
Figure 5-3 11 kV underground cable population with poor asset health
Our CBARM model of 11 kV underground cables is under development at the time of writing the AMP. In the mean-time we will focus our efforts on cables with known fault history with high criticality load and cables with poor test results to inform and prioritise our replacement programme.
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