Electricity Asset Management Plan 2019-2029
193
Vector Limited://
OVERHEAD 11 KV SWITCHGEAR RENEWAL
NEEDS STATEMENT Vector’s overhead network includes 715 rocking-post type air break switches of various designs. Of these, approximately two thirds are on the Northern network, with the remainder in the Auckland network. Until the year 2000 rocking-post type air break switches were the primary type of switch used for field switching. From 2000 to 2015 fully enclosed (SF6 gas) switches were predominantly used. Since 2015, air break switches with integral arc-interrupting devices are now the Vector standard because they are more robust and simpler to maintain. Some of the switches failed during operation by field technicians that resulted in molten metal falling onto the ground in close proximity to operators. Apart from the target to improve performance, this programme will also have safety as a targeted outcome. To address this issue, at least 365 overhead switches need to be replaced over the 10-year AMP period to prevent a deterioration of service levels. However, analysis undertaken in 2017 of air break switches against the SAIDI benefit they offer, showed that a number of switches are no longer in optimal locations in the network to offer optimum SAIDI benefit. Therefore, it is expected that rather than replacing all 365 switches, improved SAIDI benefit can be obtained by replacing 265 switches in optimum locations in the network.
TARGETED OUTCOMES
CUSTOMER EXPERIENCE
SAFETY
RELIABILITY
RESILIENCE
OPERATIONAL EFFICIENCY
CYBER SECURITY AND PRIVACY
OPTIONS CONSIDERED Options to address the need identified above have been assessed and are summarised in the following table.
DESCRIPTION
DISCUSSION OF OPTION
ESTIMATED COST (NPV IF APPLICABLE)
STATUS
Option 1: Do nothing
Looking forward we are expecting that the overhead network air break rocking-post type switches will continue to deteriorate and have a continued negative impact on SAIDI and asset safety incident rates. Failure of air break switches, most likely during operation, will continue to present a Health and Safety risk and as the switches age this risk will increase. Undertaking a staged and scheduled programme of works to replace ageing air break switches will remove the risks associated with the do-nothing option. It will also allow safe and ease of sectionalising and segmentation of the network during contingency events and during maintenance
Rejected
Option 2: Undertake a staged and scheduled programme of works to replace aging air break rocking-post type switches
$3.63M Selected
PROPOSED INVESTMENT SUMMARY ($MILLION NOMINAL)
DESCRIPTION
FY20
FY21
FY22
FY23
FY24
FY25
FY26
FY27
FY28
FY29 TOTAL
Auckland overhead 11 kV switch renewal Northern overhead 11 kV switch renewal
0.04
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
1.12
0.08
0.27
0.27
0.27
0.27
0.27
0.27
0.27
0.27
0.27
2.51
Total CAPEX
0.12
0.39
0.39
0.39
0.39
0.39
0.39
0.39
0.39
0.39
3.63
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