Electricity Asset Management Plan 2019-2029
95
Vector Limited://
at Wairau zone substation where the transformers are operated in parallel with a 220 kV/33 kV Transpower transformer 8 . Key statistics of the 110 kV subtransmission feeder assets are shown in the Table below.
No of 110 kV overhead subtransmission circuits
3
Route length of 110 kV overhead subtransmission circuits (km)
26.62
No of timber support structures for 110 kV overhead subtransmission circuits
68
No of concrete support structures for 110 kV overhead subtransmission circuits
54
No of steel support structures for 110 kV overhead subtransmission circuits
62
No of support structures that support double 110 kV overhead circuits
63
Table 4-4 Key statistics for 110 kV subtransmission network
Population and Age 98% of the conductors were installed in the 1970s and the present age is 48 years. 2% new conductors were installed in 2011 to 2012 as part the establishment of a new grid exit point at Wairau zone substation. The conductors in the three circuits are all AAC and is a mixture of 265mm² (38%) and 322mm² (62%). Condition and Health The life of the conductors is limited by its ability to maintain operating tensions developed by static (gravity) and dynamic (wind) forces. These in turn are influenced by conductor type, size, span length, sag and environmental factors (corrosive elements and exposure to wind). The conductors and poles, although ageing, are in reasonable condition. Strategy The 110 kV overhead circuits are maintained in accordance with Vector’s maintenance standard. These 110 kV circuits will not be refurbished or the conductors replaced but will be maintained and kept in service until a 2nd 220 kV/33 kV transformer is installed at Wairau zone substation which is expected within the first half of the 10-year AMP period.
4.2.4 SUBTRANSMISSION 33 KV AND 22 KV OVERHEAD LINES Overview
The 33 kV and 22 kV subtransmission overhead line network is constructed with a mix of Copper and Aluminium conductors mostly on concrete poles. The smallest Copper conductor is 70mm² and Aluminium conductors are a mix of ACSR and AAC conductors. The largest Aluminium conductor is 265mm². No covered conductor or aerial bundled conductor is used in the subtransmission network. Key statistics of the 33 kV and 22 kV subtransmission overhead lines are shown in the Table below.
No of 33 kV overhead subtransmission circuits
86
Route length of 33 kV overhead subtransmission circuits (km)
367
No of 33 kV overhead support structures
6,232
No of 22 kV overhead subtransmission circuits
1
No of 22 kV overhead support structures
21
Table 4-5 Key statistics for 33 kV and 22 kV OH subtransmission network
Population and age The graphs below summarises the population and age of our 33 kV and 22 kV subtransmission overhead line conductors and poles.
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8 Installed in 2011 – 2012 as part of the establishment of a new GXP at Wairau zone substation
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