Electricity Asset Management Plan 2019-2029
185
Vector Limited://
In 2012 a refurbishment project was undertaken on the Liverpool Merlin Gerin 110 kV switchboard to replace the most vulnerable components through which gas was leaking (e.g. switch position indicating windows and fragile carbon disk pressure relief devices) as well as overhauling the hydraulic systems of all CBs. The opportunity offered by the refurbishment was utilised to install milliampere output pressure transducers to make the switch ready for a comprehensive gas monitoring system to be installed. The layout of the 110 kV switch is such that a gas monitoring system can be installed and this needs to be undertaken. Without such a system, the switch could be shut down unnecessarily resulting in a negative impact to SAIDI/SAIFI and Security of Supply in the CBD.
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 and continue to rely on the single global gas alarm
A lack of gas-trending and reliance on a single alarm means there is a risk that the whole switch could be shu7.85tdown unnecessarily and this will have a negative impact on the SAIDI/SAIFI reliability index, security of supply to Auckland’s CBD and will impact Vector’s reputation. This strategic switch is ageing and the reliance on a global gas alarm requires intensive manual monitoring and there is no visibility of gas trending A system that provides comprehensive reporting on gas- trending and gas-alarms will provide full visibility to the EOC and negate the need for constant manual monitoring. This system will reduce the risk of high impact on the SAIDI/SAIFI index and reduce the risk of a high impact on the security of supply to the Auckland CBD
Rejected
Option 2: install a gas monitoring and trending system
$0.20M Selected
PROPOSED INVESTMENT SUMMARY ($MILLION NOMINAL)
DESCRIPTION
FY20
FY21
FY22
FY23
FY24
FY25
FY26
FY27
FY28
FY29 TOTAL
Liverpool 110 kV gas monitoring system
0.20
0.20
Total CAPEX
0.20
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.20
POWER TRANSFORMER REPLACEMENT PROGRAMME
NEEDS STATEMENT Zone substation power transformers are the key items to enable the transfer of energy from the subtransmission network to Vector’s distribution network. We have 216 power transformers in service and the oldest dates from 1950: the average age for the fleet is 32 years. Forty transformers are 50 years and older with the oldest 68 years of age. Full details of our existing fleet of zone substation power transformers and their age profiles are given in Section 4. The insulation system of power transformers consists primarily of mineral oil, paper and pressboard that has a finite life even under ideal operating conditions and ageing of the paper insulation depends primarily on the operating temperature of the oil and the length of time for operation at high oil temperatures. Moisture and the presence of oxygen are other factors that will accelerate the ageing of transformers. Another key factor in the life expectancy of a power transformer is the history of downstream faults that a transformer has been subjected to: high fault levels will cause winding and core deformation
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