Electricity Asset Management Plan 2019-2029
188
Vector Limited://
DESCRIPTION
DISCUSSION OF OPTION
ESTIMATED COST (NPV IF APPLICABLE)
STATUS
Option 1: Do nothing – do not undertake civil and structural upgrades
By postponing or not undertaking the works will result in further deterioration of buildings and structures and this will in turn result in remedial works becoming more extensive and more costly to remedy. Apart from the afore mentioned, Vector is obliged to comply with Council seismic standards within a certain time frame Timely remedial capital investment will remove the risk of further deterioration of zone substation facilities and will also reduce the risk of failure of primary and/or secondary plant inside a zone substation(s) due to failing facilities. Selecting this option also means that we will comply with regulatory and Council seismic requirements to mitigate the risk posed by non-compliant facilities during a seismic event and will then also remove the commensurate risk to operating and maintenance personnel
Rejected
Option 2: Undertake civil and structural remedial capital works
$3.83M Selected
PROPOSED INVESTMENT SUMMARY ($MILLION NOMINAL)
DESCRIPTION
FY20
FY21
FY22
FY23
FY24
FY25
FY26
FY27
FY28
FY29 TOTAL
Auckland civil structures upgrades
0.30
0.54
0.54
0.14
0.14
0.14
0.14
0.14
0.14
0.14
2.36
Northern civil structures upgrades
0.20
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
1.46
Total CAPEX
0.50
0.68
0.68
0.28
0.28
0.28
0.28
0.28
0.28
0.28
3.82
NEUTRAL EARTHING RESISTOR INSTALLATIONS IN ZONE SUBSTATIONS
NEEDS STATEMENT Our larger commercial and industrial customers have come to depend more and more on reliable electricity as an essential resource for their enterprises and we have had specific requests for 11kV bus sections at certain zone substations to be operated closed (in parallel) to ensure that supply to a customer is uninterrupted in the event of failure of one of Vector’s zone substation transformers, 11 kV bus sections or failure of one of the customer’s 11 kV supply circuits. Because of the fact that we still have a sizable population of older generation 11kV distribution cables with low rated earth screens parallel operation of 11 kV zone substations busbars is not possible at such zone substations due to the risk of more extensive damage to 11kV cables with low rated earth fault currents. On some urban 11 kV systems earth fault currents are up to 15% higher than phase fault currents and can be higher than the 250 MVA (13.1 Kiloampere) rating of typical ring main units. Neutral earthing resistors are used to limit earth fault currents in power systems. The primary effect of the installation of neutral earthing resistors is a very large decrease in the fault current when an earth fault occurs on the system. To be able to provide uninterrupted supply to large customers in the event of 11 kV bus, power transformer or 11 kV supply cable failures there is a need to install neutral earth resistors at such zone substations. Not all zone substations where this plant might be required have been identified yet so this is a capital provision that will be used as and where required.
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.
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