Electricity Asset Management Plan 2019-2029
210
Vector Limited://
routers, LAN switches, communications devices, RTUs and ageing copper pilot cables
network with sufficient reliability for the big data requirements of the future.
PROPOSED INVESTMENT SUMMARY ($MILLION NOMINAL)
DESCRIPTION
FY20
FY21
FY22
FY23
FY24
FY25
FY26
FY27
FY28
FY29 TOTAL
Auckland WAN Routers and Comms Cables Upgrade Northern WAN Routers and Comms Cables Upgrade Auckland Upgrade SCADA Coms to 11kV pole mounted switches Northern Upgrade SCADA Coms to 11kV pole mounted switches Northern microwave comms link alternative link
0.50
0.40
0.30
0.20
0.10
0.10
0.10
0.10
0.10
0.10
2.00
0.50
0.40
0.30
0.20
0.10
0.10
0.10
0.10
0.10
0.10
2.00
0.08
0.18
0.18
0.18
0.18
0.18
0.18
0.18
0.18
0.18
1.65
0.20
0.22
0.26
0.26
0.26
0.26
0.26
0.26
0.26
0.26
2.52
0.15
0.30
0.45
Northern RTU Replacement
0.10
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.55
Auckland RTU Replacement
0.20
0.20
0.20
0.20
0.20
0.20
0.20
0.20
0.20
0.20
2.00
Liverpool 110kV RTU replacement
0.15
0.15
0.30
Total CAPEX
1.73
1.75
1.44
1.24
0.89
0.89
0.89
0.89
0.89
0.89
11.47
AUCKLAND AND NORTHERN SUBTRANSMISSION AND ZONE SUBSTATION PROTECTION
NEEDS STATEMENT The subtransmission protection schemes in Vector’s network consist of subtransmission circuits that are generally radial feeds (duplicated or triplicated) to zone substations and historically used copper pilot wire protection in the Auckland network. In the Northern network ,the subtransmission is a reconfigurable meshed network that historically used distance protection at GXPs and directional protection at individual zone substations. The Auckland subtransmission protection network still has a number of electromechanical pilot wire protection schemes, which are reliant on aged copper pilots that are increasingly failing and is approaching or past anticipated end of life (40 years). Electromechanical pilot wire protection does not have supervision facilities, so asset observations can only be found through routine maintenance. As the pilot wires degrade and the relays age, there is an increasing risk that the protection relays may not operate when required to do so or may operate for out-of-zone faults. This gives an increased risk of wider- spread disturbance to the power system and potential to lose supply to entire zone substations. The Northern network currently uses distance/directional protection schemes. The Northern network has large sections of overhead lines where two subtransmission circuits share the same pole, often with underbuilt distribution circuits. This results in potential mal-operation of protection caused by mutual coupling between the circuits, or the fault spreading from one circuit to the other adjacent circuits, resulting in genuine operation of the protection. There have been a number of high SAIDI outages caused by these scenarios in recent years as there is potential to lose supply to multiple zone substations due to the meshed nature of the Northern network. Also, most of the existing distance protection relays are approaching end of life (20 years) and a number of failures have been experienced recently. There is no vendor support for electromechanical relays and it is becoming harder to find technical staff to maintain electro-mechanical line differential protection schemes that consist of multiple discreet relays. A large number of zone substations still has electromechanical and static protection systems that are all past or near end of anticipated maximum life of 40 and 20 years respectively. These systems do not have any self-monitoring, reporting or data storing capability to undertake post fault analysis and have limited alarming capability. First generation numerical relays are also approaching end of anticipated maximum life of 20 years and increased failure rate is being witnessed. These systems are more complicated to replace as they have increased (often bespoke) functionality to consider. As for subtransmission protection schemes the electromechanical protection in zone substations are no longer supported by suppliers and spares are difficult to get hold of. Furthermore, electromechanical relays have moving parts that can lose their calibration and thus protection sensitivity over time.
Quay Street 22 kV substation is a critical node within Auckland’s CBD and supplies amongst others electricity to the Ports of Auckland and Parnell. It is not able to have suitable protection settings applied to the bus section CB to allow grading
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